Implants for Altering Wear Patterns of Articular Surfaces

ABSTRACT

Methods and devices for correcting wear pattern defects in joints. The methods and devices described herein allow for the restoration of correcting abnormal biomechanical loading conditions in a joint brought on by wear pattern defects, and also can, in embodiments, permit correction of proper kinematic movement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/935,965 filed Nov. 9, 2015 and entitled “Implants for Altering WearPatterns of Articular Surfaces,” which in turn is a continuation of U.S.application Ser. No. 14/222,836 filed Mar. 24, 2014 and entitled“Implants for Altering Wear Patterns of Articular Surfaces,” which inturn is a divisional of U.S. application Ser. No. 12/398,598 filed Mar.5, 2009 and entitled “Implants for Altering Wear Patterns of ArticularSurfaces,” which in turn claims priority to U.S. Provisional Application61/034,035 filed Mar. 5, 2008 and entitled “Wear Pattern-OptimizedArticular Implants.” Each of the above described applications is herebyincorporated herein by reference.

FIELD OF THE INVENTION

The embodiments described herein relate to orthopedic methods, systemsand devices. In particular, new methods, systems and devices forarticular resurfacing in joints including the knee are provided.

BACKGROUND

There are various types of cartilage, e.g., hyaline, elastic andfibrocartilage. Hyaline cartilage is found at the articular surfaces ofbones, e.g., in the joints, and is responsible for providing the smoothgliding motion characteristic of movable joints. Articular cartilage isfirmly attached to the underlying bones and measures typically less than5 mm in thickness in human joints, with considerable variation dependingon the joint and the site within the joint.

Adult cartilage has a limited ability of repair; thus, damage tocartilage produced by disease, such as rheumatoid and/or osteoarthritis,or trauma, can lead to serious physical deformity and debilitation.Furthermore, as human articular cartilage ages, its tensile propertieschange and the cartilage tends to wear away. The superficial zone of theknee articular cartilage exhibits an increase in tensile strength up tothe third decade of life, after which it decreases markedly with age asdetectable damage to type II collagen occurs at the articular surface.The deep zone cartilage also exhibits a progressive decrease in tensilestrength with increasing age, although collagen content does not appearto decrease. These observations indicate that there are changes inmechanical and, hence, structural organization of cartilage with agingthat, if sufficiently developed, can predispose cartilage to traumaticdamage.

In osteoarthritis, human joints such as the knee, hip, ankle, footjoints, shoulder, elbow, wrist, hand joints, and spinal joints tend towear away the articular cartilage. The wear is frequently not uniform,but localized to a defined region within a joint. For example, in a kneejoint, the wear can be on a medial or lateral femoral condyle, a medialor lateral tibial plateau, a medial or lateral trochlea, a medial facet,lateral facet or median ridge of the patella. In a hip joint, the wearcan be on an acetabulum or a femoral head or both.

Generally, wear can be limited to one articular surface or it can affectmultiple articular surfaces. Wear can occur in one or more subregions onthe same articular surface or multiple articular surfaces.

In a medial femoral condyle or medial tibial plateau, wear can occur inan anterior, central or posterior portion of the articular surface. Wearcan also occur in a medial or lateral portion of an articular surface.In a lateral femoral condyle or lateral tibial plateau, wear can occurin an anterior, central or posterior portion of the articular surface.Wear can also occur in a medial or lateral portion of an articularsurface. In a femoral head or acetabulum, wear can occur in an anterior,posterior, medial or lateral, superior or inferior location.

In short, any location of wear is possible, and any combination of wearpatterns on the same articular surface and opposing articular surfacesis possible.

Wear starts typically in the articular cartilage, but it can then extendinto the subchondral bone and marrow cavity. Wear can be accompanied bycartilage loss, subchondral sclerosis, subchondral cyst formation,osteophyte formation, bone marrow edema.

Wear is frequently the result of an abnormal biomechanical loadingcondition in a joint. While modern arthroplasty surgery attempts tocorrect such abnormal biomechanical loading conditions in a joint, someresidual biomechanical loading abnormality or new biomechanical loadingabnormality is frequently present after partial or total jointreplacement surgery.

Abnormal biomechanical loading of joint implants is a frequent cause forimplant failure since current implants cannot account for the increasedloads and stresses resulting from such abnormal loading.

Usually, severe damage or cartilage loss is treated by replacement ofthe joint with a suitable prosthetic material, most frequently metalalloys. See, e.g., U.S. Pat. Nos. 6,383,228; 6,203,576; and 6,126,690.As can be appreciated, joint arthroplasties are highly invasive andrequire surgical resection of the entire (or a majority of) thearticular surface of one or more bones involved in the repair. Typicallywith these procedures, the marrow space is fairly extensively reamed inorder to fit the stem of the prosthesis within the bone. Reaming resultsin a loss of the patient's bone stock, and over time subsequentosteolysis will frequently lead to loosening of the prosthesis. Further,the area where the implant and the bone mate degrades over timerequiring the prosthesis to eventually be replaced. Since the patient'sbone stock is limited, the number of possible replacement surgeries isalso limited for joint arthroplasty. In short, over the course of 15 to20 years, and in some cases even shorter time periods, the patient canrun out of therapeutic options ultimately resulting in a painful,nonfunctional joint.

SUMMARY

The embodiments described herein are directed to providing methods anddevices for correcting wear pattern defects in joints. They provide forimproved, and, in some embodiments, optimized or ideal, implant systemsto correct or manage abnormal wear patterns. Some of the methods anddevices described herein allow for the correction of abnormalbiomechanical loading conditions in a joint brought on by wear patterndefects, and also can, in embodiments, permit correction of properkinematic movement. Abnormal biomechanical loading of conventional jointimplants is a frequent cause for implant failure, since current implantdesigns are unable to account for the increased loads and stressesresulting from such abnormal loading. Alternatively, the methods anddevices described herein allow for the accommodation of abnormalbiomechnical loading conditions in the shape of the implant system, thusreducing the forces on the implant that can lead to implant failure.

One embodiment is a method for designing an orthopedic device thatalters a wear pattern on an articular surface of a joint. The method mayinclude receiving image data associated with the joint, e.g., via acomputer network; determining a wear pattern of an articular surface atleast in part from the image data; and designing an orthopedic devicebased at least in part on the image data. The orthopedic device can bedesigned to alter the wear pattern of the articular surface to a revisedwear pattern.

Other embodiments may include one or more of the following. Thealteration may be a change to or an improvement over the existing wearpattern, or the wear pattern can be optimized to provide an ideal wearpattern. The image data may be derived from a technique selected fromthe group consisting of arthroscopy, arthrotomic examination, gaitanalysis, and imaging analysis; or a combination thereof.

The step of designing can include, for example, altering the wearpattern at least in part by adjusting the location of the wear patternon the articular surface; altering the wear pattern at least in part bydistributing the load that will be placed on the articular surface; oraltering the wear pattern at least in part by reducing point loading onthe articular surface.

The wear pattern can be determined automatically, semi-automatically, ormanually.

The method can further include determining a second wear pattern of asecond articular surface of the joint from the image data. Theorthopedic device can be designed based at least in part on the imagedata associated with the second articular surface, and the orthopedicdevice can be designed to alter the second wear pattern of the secondarticular surface to a second revised wear pattern. The orthopedicdevice can be, for example, a bicompartmental resurfacing device for aknee.

A second wear pattern of a second articular surface of the joint can bedetermined from the image data. A second orthopedic device can be basedat least in part on the image data associated with the second articularsurface, and the second orthopedic device can be designed to alter thesecond wear pattern of the second articular surface to a second revisedwear pattern. For example, the first orthopedic device can be a tibialtray for a knee and the second orthopedic device can be a second tibialtray for another compartment of the knee.

A second orthopedic device can be designed based at least in part on theimage data, and it can be designed to alter the wear pattern of thearticular surface to the revised wear pattern. For example, the firstorthopedic device can be a tibial tray for a knee joint and the secondorthopedic device can be a unicompartmental femoral resurfacing devicefor the knee joint. The two implants can be designed to be complimentaryand thereby affect the alteration in the wear pattern as designed.

The orthopedic device can be many different types of devices such as areplacement hip joint or a knee replacement device including a femoralcomponent and a tibial component. The orthopedic device can be designedusing a library of design elements.

The orthopedic device can be designed to include at least one surfacethat conforms to an existing surface of the joint (see, e.g., U.S.patent application Ser. No. 10/997,407, filed Nov. 24, 2004, which isincorporated herein by reference in its entirety). The orthopedic devicecan be designed to include at least one surface that is derived from anexisting surface of the joint. For example, the derived surface canexclude a defect of the existing surface, it can approximate an idealsurface of the joint, and it can approximate a healthy surface of thejoint. Similarly, the orthopedic device can be designed to include atleast one curve derived from an existing surface of the joint. Forexample, the curve can exclude a defect of the existing joint, it canapproximate an ideal curve of the joint, and it can approximate ahealthy surface of the joint. The orthopedic device also can be designedto include at least one dimension that is derived from an existingdimension of the joint. For example, the derived dimension can exclude adefect of the existing joint, it can approximate an ideal dimension ofthe joint, and it can approximate a dimension associated with a healthyjoint.

The orthopedic device can be designed to be placed at least in part oncartilage associated with the joint, and it can be designed to be placedat least in part on subchondral bone associated with the joint. It canalso be designed to be placed on other types of tissue or combinationsof tissue.

The method can also include the production of the orthopedic device. Forexample, the orthopedic device can be produced using traditional methodssuch as casting or newer technologies, such as direct digitalmanufacturing. As an alternate example, the orthopedic device can beproduced by tailoring a precursor orthopedic device, which may be, e.g.,selected from a library of orthopedic devices. Similarly, the orthopedicdevice can be produced by altering a standard orthopedic device, whichmay be, e.g., selected from an inventory of orthopedic devices

Another embodiment is a method for preparing an implant for correctingan articular surface wear pattern that includes obtaining an image of anarticular surface; analyzing the image for the presence or absence ofwear pattern indicia; determining a wear pattern from the wear patternindicia; and providing an implant having a characteristic topography forcorrecting the wear pattern. The implant can have an interior surfaceand an outer surface. The interior surface may be a mirror image of thearticular surface.

An implant for correcting an articular surface wear pattern, comprisingan implant body having a characteristic topography, an interior surface,and an outer surface, where the implant body topography is derived froma wear pattern analysis of the articular surface. The implant caninclude an interior surface is a mirror image of the articular surface.

Another embodiment is a method of joint arthroplasty that includes:obtaining an image of a surface of a joint; the surface of the jointincluding a wear pattern; deriving a shape of the joint surface based,at least in part, on the image; and providing an implant having asurface based on the surface of the joint. The implant can be configuredto alter the wear pattern of the joint.

Other embodiments may include one or more of the following. Obtainingthe image can include an imaging technique selected from the groupconsisting of x-ray imaging and processing; fluoroscopy; digitaltomosynthesis; ultrasound; optical coherence, conventional, cone beam,or spiral computed tomography (CT); single photon emission tomography(SPECT); bone scan; positron emission tomography (PET); magneticresonance imaging (MRI); thermal imaging; and optical imaging, or acombination thereof. The joint can be any joint with an articularsurface, for example, a knee, a shoulder, a hip, a vertebrae, an elbow,an ankle, a foot, a toe, a hand, a wrist and a finger. The wear patterncan be based, at least in part, on one of a presence, absence, location,distribution, depth, area, or dimensions of cartilage loss; presence,absence, location, distribution, depth, area, or dimensions ofsubchondral cysts; presence, absence, location, distribution, depth,area, or dimensions of subchondral sclerosis; presence, absence,location, distribution, volume, area, depth or dimensions of asubchondral bone plate abnormality; presence, absence, location,distribution, or dimensions of a subchondral bone deformity; presence,absence, or severity of a varus or valgus deformity; presence, absenceor severity of recurvatum or antecurvatum; and presence, absence,location, distribution, volume, depth or dimensions of bone marrowedema. The surface of the implant can be substantially at least one ofrigid, non-pliable, non-flexible and non-resilient, and can be made ofvarious suitable materials or combinations of materials, e.g., polymer,a cross-linked polymer, a ceramic, a metal, an alloy, and aceramic-metal composite.

In another embodiment, a wear pattern is determined pre-operatively orintraoperatively. Wear patterns may be assessed by, e.g.: arthroscopy;arthrotomy; imaging tests such as x-ray imaging; fluoroscopy; digitaltomosynthesis; cone beam, conventional and spiral CT; bone scan; SPECTscan; PET; MRI; thermal imaging; optical imaging; and any other currentand future technique for detecting articular wear; optical coherencetomography; gait analysis; and techniques merging information from oneor more of these tests. Many modifications and derivatives of theseimaging tests can be used. For example, with MRI, images can be visuallyinterpreted for assessing cartilage loss or bone deformity.Alternatively, computer methods including maps of cartilage thicknesscan be utilized for this purpose. Alternatively, a scan reflectingbiomechanical composition of the articular cartilage can be performed.These include, but are not limited to, dGEMRIC, T1 Rho, and T2 scans.

Different scanning methods within the same modalities and/or differentmodalities can be combined in order to determine one or more wearpatterns.

In one embodiment, a wear pattern can be determined and an implant canbe designed or selected that is adapted or optimized for a patient'swear pattern. Such adaptations or optimizations can include in the areaof the wear pattern or areas adjacent to a wear pattern: decrease inmaterial thickness; increase in material thickness; change in materialcomposition; change in cross-linking properties, e.g., via localexposure to Gamma radiation or other cross-linking reagents; change inimplant shape, e.g., change in convexity or concavity of one or moresurface in one or more dimensions; enhanced matching of shape betweentwo mating articular surfaces (enhanced constraint); decreased matchingof shape between two mating articular surfaces (decreased constraint).

In one embodiment, an implant can be designed for a wear patternmeasured in a patient.

In another embodiment, a wear pattern can be measured in a patient andan implant with a matching wear pattern design can be selected from alibrary of pre-manufactured implants.

In yet another embodiment, a wear pattern-specific implant shape orgeometry is achieved using a number of manufacturing techniques,including, but not limited to: polishing; milling; machining; casting;rapid protocasting; laser sintering; laser melting, and electroabrasion.

In one embodiment, the wear pattern-adapted articular surface is formedde novo. In another embodiment, the wear pattern-adapted articularsurface of the implant is achieved by processing an implant with astandard shape of the articular surface (a “blank”) and adapting theshape for a patients' wear pattern, e.g., using machining orelectroabrasion.

In another embodiment, methods for preparing an implant for correctingor accommodating an articular surface wear pattern are disclosed,wherein an image of an articular surface is obtained; the image isanalyzed for the presence or absence of wear pattern indicia; a wearpattern is determined from the wear pattern indicia; and an implant withan inferior surface and a superior surface is provided, having acharacteristic topography for correcting or accommodating the wearpattern.

In yet another embodiment, an implant is disclosed for correcting oraccommodating an articular surface wear pattern, including an implantbody having a characteristic topography, an inferior surface, and asuperior surface, where the implant body topography is derived from awear pattern analysis of the articular surface.

In another embodiment, a method of joint arthroplasty includes obtainingan image of a surface of a joint, the surface of the joint including awear pattern. A shape of the joint surface is derived based, at least inpart, on the image. An implant is provided having a surface that eitherconforms with or duplicates the surface of the joint.

In related embodiments, obtaining the image may include x-ray imagingand processing; fluoroscopy; digital tomosynthesis; ultrasound; opticalcoherence, conventional, cone beam, or spiral computed tomography (CT);single photon emission tomography (SPECT); bone scan; positron emissiontomography (PET); magnetic resonance imaging (MRI); thermal imaging; oroptical imaging, or a combination thereof. The joint may be a knee,shoulder, hip, vertebrae, elbow, ankle, foot, toe, hand, wrist orfinger. The wear pattern may be determined based, at least in part, on:a presence, absence, location, distribution, depth, area, or dimensionsof cartilage loss; presence, absence, location, distribution, depth,area, or dimensions of subchondral cysts; presence, absence, location,distribution, depth, area, or dimensions of subchondral sclerosis;presence, absence, location, distribution, volume, area, depth ordimensions of a subchondral bone plate abnormality; presence, absence,location, distribution, or dimensions of a subchondral bone deformity;presence, absence, or severity of a varus or valgus deformity; presence,absence or severity of recurvatum or antecurvatum; and/or presence,absence, location, distribution, volume, depth or dimensions of bonemarrow edema. The surface of the implant may be substantially rigid,non-pliable, non-flexible and/or non-resilient. The surface of theimplant may include a polymer, a cross-linked polymer, a ceramic, ametal, an alloy and/or a ceramic-metal composite. Providing the surfaceof the implant may include rapid prototyping, laser cutting, lasersintering, electron beam melting, casting and/or milling. The method mayfurther include positioning the implant adjacent an implantation site.The surface of the implant may be shaped prior to positioning theimplant adjacent the implantation site.

In accordance with another embodiment, an implant for joint arthroplastyincludes an implant surface that either conforms to or duplicates ajoint surface, the joint surface including a wear pattern.

In related embodiments, the implant surface may be substantially rigid,non-flexible, and/or non-pliable. The surface of the implant maybe apolymer, a cross-linked polymer, a ceramic, a metal, an alloy and/or aceramic-metal composite. The implant surface may reflect a surface ofthe joint obtained from an image.

Novel devices and methods for correcting or accommodating wear patternsin joint surfaces, e.g., cartilage, meniscus and/or bone, are thusdescribed. Advantageously, the implant has an anatomic or near-anatomicfit with the surrounding structures and tissues, thus minimizing bonecutting. In embodiments, devices provided herein also improve theanatomic functionality of the repaired joint by restoring the naturalknee joint anatomy and kinematics. This, in turn, leads to an improvedfunctional result for the repaired joint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a method for assessing a joint in need ofrepair wherein the existing joint surface is unaltered, or substantiallyunaltered, prior to receiving the selected implant. FIG. 1B is a blockdiagram of a method for assessing a joint in need of repair accordingwherein the existing joint surface is unaltered, or substantiallyunaltered, prior to designing an implant suitable to achieve the repair.FIG. 1C is a block diagram of a method for developing an implant andusing the implant in a patient.

FIG. 2A is a perspective view of a joint implant suitable forimplantation at the tibial plateau of the knee joint. FIG. 2B is a topview of the implant of FIG. 2A. FIG. 2C is a cross-sectional view of theimplant of FIG. 2B along the lines C-C shown in FIG. 2B. FIG. 2D is across-sectional view along the lines D-D shown in FIG. 2B. FIG. 2E is across-sectional view along the lines E-E shown in FIG. 2B. FIG. 2F is aside view of the implant of FIG. 2A. FIG. 2G is a cross-sectional viewof the implant of FIG. 2A shown implanted taken along a plane parallelto the sagittal plane. FIG. 2H is a cross-sectional view of the implantof FIG. 2A shown implanted taken along a plane parallel to the coronalplane. FIG. 2I is a cross-sectional view of the implant of FIG. 2A shownimplanted taken along a plane parallel to the axial plane. FIG. 2J showsa slightly larger implant that extends closer to the bone medially(towards the edge of the tibial plateau) and anteriorly and posteriorly.FIG. 2K is a side view of an alternate embodiment of the joint implantof FIG. 2A showing an anchor in the form of a keel. FIG. 2L is a bottomview of an alternate embodiment of the joint implant of FIG. 2A showingan anchor. FIG. 2M shows an anchor in the form of a cross-member. FIGS.2N-1, 2N-2, 2O-1 and 2O-2 are alternative embodiments of the implantshowing the lower surface have a trough for receiving a cross-bar. FIG.2P illustrates a variety of cross-bars. FIGS. 2Q-R illustrate the deviceimplanted within a knee joint. FIGS. 2S(1-9) illustrate another implantsuitable for the tibial plateau further having a chamfer cut along oneedge. FIG. 2T(1-8) illustrate an alternate embodiment of the tibialimplant wherein the surface of the joint is altered to create a flat orangled surface for the implant to mate with.

FIGS. 3A and B are perspective views of a joint implant suitable for useon a condyle of the femur from the inferior and superior surfaceviewpoints, respectively. FIG. 3C is a side view of the implant of FIG.3A. FIG. 3D is a view of the inferior surface of the implant; FIG. 3E isa view of the superior surface of the implant and FIG. 3F is across-section of the implant. FIG. 3G is an axial view of a femur withthe implant installed thereon. FIG. 3H is an anterior view of the kneejoint without the patella wherein the implant is installed on thefemoral condyle. FIG. 3I is an anterior view of the knee joint with animplant of FIG. 3A implanted on the femoral condyle along with animplant suitable for the tibial plateau, such as that shown in FIG. 2.FIGS. 3J-K illustrate an alternate embodiment of a joint implant for useon a condyle of a femur further having at least one chamfer cut. FIG. 4Aillustrates an implant suitable for the femoral condyle according to theprior art. FIGS. 4B-I depict another implant suitable for placement on afemoral condyle. FIG. 4B is a slightly perspective view of the implantfrom the superior surface. FIG. 4C is a side view of the implant of FIG.4B. FIG. 4D is a top view of the inferior surface of the implant; FIGS.4E and F are perspective side views of the implant. FIG. 4G is an axialview of a femur with the implant installed thereon. FIG. 4H is ananterior view of the knee joint without the patella wherein the implantis installed on the femoral condyle. FIG. 4I is an anterior view of theknee joint with an implant of FIG. 4B implanted on the femoral condylealong with an implant suitable for the tibial plateau, such as thatshown in FIG. 2.

FIGS. 5A-S are depictions of another implant suitable for placement onthe femoral condyle. FIG. 5A is a top view of the inferior surface ofthe implant showing a chamfer cut. FIG. 5B is a slightly perspectiveview of the superior surface of the implant. FIG. 5C is a perspectiveside view of the implant from a first direction; FIG. 5D is a slightlyperspective side view of the implant from a second direction. FIGS. 5E-Fare side views of the implant showing the bearing loads; FIGS. 5G and Hillustrate an alternative embodiment wherein the implant has lateralrails; FIG. 5I illustrates another embodiment wherein the implant has ananchoring keel. FIG. 5J is an axial view of a femur with the implantinstalled on the femoral condyles. FIG. 5K is an anterior view of theknee joint without the patella wherein the implant is installed on thefemoral condyle. FIG. 5L is an anterior view of the knee joint with animplant of FIG. 5A implanted on the femoral condyles along with animplant suitable for the tibial plateau, such as that shown in FIG. 2.FIGS. 5M-N depicts a device implanted within the knee joint. FIG. 5Odepicts an alternate embodiment of the device which accommodates anpartial removal of the condyle. FIGS. 5P-S illustrate alternativeembodiments of the implant having one or more chamfer cuts.

FIGS. 6A-G illustrate a device as shown in FIG. 5 along with a graphicalrepresentation of the cross-sectional data points comprising the surfacemap.

FIGS. 7A-C illustrate an alternate design of a device, suitable for aportion of the femoral condyle, having a two piece configuration.

FIGS. 8A-J depict a whole patella (FIG. 8A) and a patella that has beencut in order to install an implant (FIG. 8B). A top and side view of asuitable patella implant is shown (FIGS. 8C-D), and an illustration ofthe implant superimposed on a whole patella is shown to illustrate thelocation of the implant dome relative to the patellar ridge. FIGS. 8E-Fillustrate the implant superimposed over a patella. FIGS. 8G-Jillustrate an alternate design for the patella implant based on a blank(FIG. 8G).

FIGS. 9A-C depict representative side views of a knee joint with any ofthe devices taught installed therein. FIG. 9A depicts the knee with acondyle implant and a patella implant. FIG. 9B depicts an alternate viewof the knee with a condyle implant and a patella implant wherein thecondyle implant covers a greater portion of the surface of the condylein the posterior direction. FIG. 9C illustrates a knee joint wherein theimplant is provided on the condyle, the patella and the tibial plateau.

FIGS. 10A-D depict a frontal view of the knee joint with any of thedevices taught installed therein. FIG. 10A depicts the knee with atibial implant. FIG. 10B depicts the knee with a condyle implant. FIG.10C depicts a knee with a tibial implant and a condyle implant. FIG. 10Cdepicts a knee with a bicompartmental condyle implant and a tibialimplant.

FIG. 11 illustrates in cross-section an embodiment for the hip featuringa wear pattern correcting resurfacing implant for the femoral head.

FIG. 12 illustrates a glenoid component embodiment featuring an inferiorwear pattern correcting surface 1228.

FIG. 13 illustrates a glenoid component embodiment featuring an superiorwear pattern correcting surface 1328.

FIGS. 14-16 illustrate, in simplified coronal view, a tibia with medial,lateral and central lateral tibial plateau wear patterns, and a lateraltibial plateau implant featuring a wear pattern correcting surface foreach respective type of wear pattern.

FIGS. 17-19 illustrate, in simplified sagittal view, a tibia withmedial, lateral and central lateral tibial plateau wear patterns, and alateral tibial plateau implant featuring a wear pattern correctingsurface for each respective type of wear pattern.

DETAILED DESCRIPTION

The devices and methods described herein may replace all or a portion(e.g., diseased area and/or area slightly larger than the diseased area)of the articular surface, and achieve an anatomic or near anatomic fitwith the surrounding structures and tissues. Where the devices and/ormethods include an element associated with the underlying articularbone, the bone-associated element can achieve a near anatomic alignmentwith the bone. The articular surface may include the superior bonesurface of bone ends. For example, the articular surfaces of the kneewould include the femoral condyles and the tibial plateau. Healthyarticular surfaces would generally be covered by cartilage, but indiseased or worn joints, the articular surface may include areas ofexposed bone.

Some embodiments provide methods and devices for repairing joints(including bone end interfaces of the knee, hip, ankle, foot, shoulder,elbow, wrist, hand and spine), particularly for repairing articularsurfaces and for facilitating integration of an articular surface repairimplant into a subject. The repair may be, without limitation, acartilage repair/resurfacing implant, a partial joint implant and/or atotal joint implant on a single joint surface or multiple jointsurfaces. Among other things, the techniques described herein allow forthe customization of the implant to suit a particular subject,particularly in terms of correcting or accommodating a wear pattern onthe articular size, cartilage thickness and/or curvature. In selectedembodiments, the interior surface of the implant is a mirror image ofthe articular surface, i.e., it is an exact or near anatomic fit,further enhancing the success of repair is enhanced. The implant isdesigned to incorporate a wear pattern analysis based, on, e.g.,electronic images of the articular surface. Some embodiments provide,e.g., minimally invasive methods for partial joint replacement,requiring only minimal or, in some instances, no loss in bone stock.Additionally, unlike with current techniques, the methods describedherein will help to restore the integrity of the articular surface byachieving an exact or near anatomic match between the implant and thesurrounding or adjacent cartilage and/or subchondral bone.

Methods for Measuring a Wear Pattern

In one embodiment, a wear pattern is determined pre-operatively orintraoperatively. Wear patterns may be assessed by, e.g.: arthroscopy;arthrotomy; imaging tests such as x-ray imaging; fluoroscopy; digitaltomosynthesis; cone beam, conventional and spiral CT; bone scan; SPECTscan; PET; MRI; thermal imaging; optical imaging; and any other currentand future technique for detecting articular wear; optical coherencetomography; gait analysis; and techniques merging information from oneor more of these tests.

Many modifications and derivatives of these imaging tests can be used.For example, with MRI, images can be visually interpreted for assessingcartilage loss or bone deformity. Alternatively, computer methodsincluding maps of cartilage thickness can be utilized for this purpose.Alternatively, a scan reflecting biomechanical composition of thearticular cartilage can be performed. These include, but are not limitedto, dGEMRIC, T1Rho, and T2 scans.

Different scanning methods within the same modalities and/or differentmodalities can be combined in order to determine one or more wearpatterns.

Wear patterns may include individual or continuous areas of surfacewear, disease or degradation. In some instances the wear pattern may belikened to a map of the articular surface wherein wear pattern indiciaare highlighted, marked or otherwise denoted, to indicate the wearpattern. Wear pattern indicia may include the: presence, absence,location, distribution, depth, area, or dimensions of cartilage loss;presence, absence, location, distribution, depth, area, or dimensions ofsubchondral cysts; presence, absence, location, distribution, depth,area, or dimensions of subchondral sclerosis; presence (e.g., thickeningor thinning), absence, location, distribution, volume, area, depth ordimensions of a subchondral bone plate abnormality; presence, absence,location, distribution, or dimensions of a subchondral bone deformity;presence, absence, or severity of a varus or valgus deformity; presence,absence or severity of another articular axis deformity, e.g.,recurvatum, antecurvatum; or presence, absence, location, distribution,volume, depth or dimensions of bone marrow edema.

Parameters for Determining a Wear Pattern

A wear pattern can be detected, for example, by determining: presence orabsence of cartilage loss; location of cartilage loss; distribution ofcartilage loss; depth of cartilage loss; area of cartilage loss; widthor dimensions of cartilage loss; presence or absence of subchondralcysts; location of subchondral cysts; distribution of subchondral cysts;volume of subchondral cysts; area of subchondral cysts; presence orabsence of subchondral sclerosis; location of subchondral sclerosis;distribution of subchondral sclerosis; volume of subchondral sclerosis;area of subchondral sclerosis; depth or width or dimensions ofsubchondral sclerosis; presence or absence of abnormality of subchondralbone plate (e.g., thickening or thinning); location of abnormality ofsubchondral bone plate; distribution of abnormality of subchondral boneplate; volume of abnormality of subchondral bone plate; area ofabnormality of subchondral bone plate; depth of abnormality ofsubchondral bone plate; width or dimensions of abnormality ofsubchondral bone plate; presence or absence of deformity of subchondralbone; location of deformity of subchondral bone; distribution ofdeformity of subchondral bone; area of deformity of subchondral bone;dimensions of deformity of subchondral bone; presence of absence ofvarus or valgus deformity; severity of varus or valgus deformity;presence or absence of other articular axis deformity, e.g., recurvatum,antecurvatum; severity of other articular axis deformity, e.g.,recurvatum, antecurvatum; presence or absence of bone marrow edema;location of bone marrow edema; distribution of bone marrow edema; volumeof bone marrow edema; area of bone marrow edema; depth of bone marrowedema; or dimensions of bone marrow edema.

One or more of these parameters can be measured preoperatively orintraoperatively. Combinations of parameters can be measured. Linear ornon-linear weightings can be applied. Mathematical and statisticalmodeling can be used to derive a wear pattern using one or more of theseparameters or combinations of parameters.

Other parameters can be measured such as presence and severity ofligament tears, muscle strength, body mass index, anthropometricparameters and the like.

Other parameters can include estimated or measured location ofligaments, e.g., medial or lateral collateral ligaments, ACL and PCL,ligamentum capitis femoris, transverse ligament, rotator cuff, spinousligaments and the like.

These data can be used to improve the localization of a wear pattern.They can also be used to derive risk models of future implant wear.

The resultant information can be used to change or adapt and implantdesign or to derive an entirely new implant design adapted to apatient's wear pattern.

Influence on implant design or selection

In one embodiment, a wear pattern can be determined and an implant canbe designed or selected that is adapted or optimized for a patient'swear pattern. Such adaptations or optimizations can include in the areaof the wear pattern or areas adjacent to a wear pattern: decrease inmaterial thickness; increase in material thickness; change in materialcomposition; change in cross-linking properties, e.g., via localexposure to Gamma radiation or other cross-linking reagents; change inimplant shape, e.g., change in convexity or concavity of one or moresurface in one or more dimensions; enhanced matching of shape betweentwo mating articular surfaces (enhanced constraint); decreased matchingof shape between two mating articular surfaces (decreased constraint).The implant may be strengthened in, without limitation, in the area ofthe wear pattern or areas adjacent to the wear pattern. The implant maybe adapted in shape to more evenly distribute load, for example, toareas of less wear.

Changes in material composition can include the use of differentmaterials, e.g., different metals or plastics or ceramics or select useof one or more of these materials in an area of wear pattern or adjacentto an area of wear pattern. Alternatively, select change in materialproperties of the same material can be used. For example, when a polymermaterial is used, select cross-linking of polymers can be performed inan area of or adjacent to a wear pattern. Such select cross-linking can,for example, be achieved, with a focused radiation beam, that is focusedon the area of wear pattern, or adjacent to wear pattern.

Gradients in material composition and properties extending from an areaof wear pattern to areas outside the wear pattern are possible.

Advantages of the devices and methods disclosed herein include (i)customization of joint repair, thereby enhancing the efficacy andcomfort level for the patient following the repair procedure; (ii) insome embodiments, eliminating the need for a surgeon to measure thedefect to be repaired intraoperatively; (iii) eliminating the need for asurgeon to shape the material during the implantation procedure; (iv)providing methods of evaluating curvature or shape of the repairmaterial based on bone or tissue images or based on intraoperativeprobing techniques; (v) providing methods of repairing joints with onlyminimal or, in some instances, no loss in bone stock; (vi) improvingpostoperative joint congruity; (vii) improving the postoperative patientrecovery in some embodiments, (viii) improving postoperative function,such as range of motion and joint kinematics and (ix) improving loadingconditions on the implant and thus reducing risk of implant failure.

I. Assessment of Joints and Alignment

The methods and compositions described herein can be used to treatdefects resulting from disease of the cartilage (e.g., osteoarthritis),bone damage, cartilage damage, trauma, and/or degeneration due tooveruse or age. The size, volume and shape of the area of interest mayinclude only the region of cartilage that has the defect, but preferablyincludes contiguous parts of the cartilage surrounding the cartilagedefect.

Size, curvature and/or thickness measurements can be obtained using anysuitable technique. For example, one-dimensional, two-dimensional,and/or three-dimensional measurements can be obtained using suitablemechanical means, laser devices, electromagnetic or optical trackingsystems, molds, materials applied to the articular surface that hardenand “memorize the surface contour,” and/or one or more imagingtechniques known in the art. Measurements can be obtained non-invasivelyand/or intraoperatively (e.g., using a probe or other surgical device).As will be appreciated, the thickness of the repair device can vary atany given point depending upon patient's anatomy and/or the depth of thedamage to the cartilage and/or bone to be corrected at any particularlocation on an articular surface.

FIG. 1A is a flow chart showing steps taken by a practitioner inassessing a joint. First, a practitioner obtains a measurement of atarget joint 10. The step of obtaining a measurement can be accomplishedby taking an image of the joint. This step can be repeated, asnecessary, 11 to obtain a plurality of images in order to further refinethe joint assessment process. Once the practitioner has obtained thenecessary measurements, the information is used to generate a modelrepresentation of the target joint being assessed 30. This modelrepresentation can be in the form of a topographical map or image. Themodel representation of the joint can be in one, two, or threedimensions, and can include a physical model. More than one model can becreated 31, if desired. Either or both the original or a subsequentlycreated model can be used. After the model representation of the jointis generated 30, the practitioner can optionally generate a projectedmodel representation of the target joint in a corrected condition 40,e.g., from the existing cartilage on the joint surface, by providing amirror of the opposing joint surface, or a combination thereof. Again,this step can be repeated 41, as necessary or desired. Using thedifference between the topographical condition of the joint and theprojected image of the joint, the practitioner can then select a jointimplant 50 that is suitable to achieve the corrected joint anatomy. Theselection process 50 can be repeated 51 as often as desired to achievethe desired result. Additionally, it is contemplated that a practitionercan obtain a measurement of a target joint 10 by obtaining, for example,an x-ray, and then select a suitable joint replacement implant 50.

As will be appreciated, the practitioner can proceed directly from thestep of generating a model representation of the target joint 30 to thestep of selecting a suitable joint replacement implant 50 as shown bythe arrow 32. Additionally, following selection of suitable jointreplacement implant 50, the steps of obtaining measurement of targetjoint 10, generating model representation of target joint 30 andgenerating projected model 40, can be repeated in series or parallel asshown by the flow 24, 25, 26.

FIG. 1B is an alternate flow chart showing steps taken by a practitionerin assessing a joint. First, a practitioner obtains a measurement of atarget joint 10. The step of obtaining a measurement can be accomplishedby taking an image of the joint. This step can be repeated, asnecessary, 11 to obtain a plurality of images in order to further refinethe joint assessment process. Once the practitioner has obtained thenecessary measurements, the information is used to generate a modelrepresentation of the target joint being assessed 30. This modelrepresentation can be in the form of a topographical map or image. Themodel representation of the joint can be in one, two, or threedimensions. The process can be repeated 31 as necessary or desired, andcan include a physical model. After the model representation of thejoint is assessed 30, the practitioner can optionally generate aprojected model representation of the target joint in a correctedcondition 40. This step can be repeated 41 as necessary or desired.Using the difference between the topographical condition of the jointand the projected image of the joint, the practitioner can then design ajoint implant 52 that is suitable to achieve the corrected jointanatomy, repeating the design process 53 as often as necessary toachieve the desired implant design. The practitioner can also assesswhether providing additional features, such as rails, keels, lips, pegs,cruciate stems, or anchors, cross-bars, etc., will enhance the implants'performance in the target joint.

As will be appreciated, the practitioner can proceed directly from thestep of generating a model representation of the target joint 30 to thestep of designing a suitable joint replacement implant 52 as shown bythe arrow 38. Similar to the flow shown above, following the design of asuitable joint replacement implant 52, the steps of obtainingmeasurement of target joint 10, generating model representation oftarget joint 30 and generating projected model 40, can be repeated inseries or parallel as shown by the flow 42, 43, 44.

FIG. 1C is a flow chart illustrating the process of selecting an implantfor a patient. First, using the techniques described above or thosesuitable and known in the art, the size of area of diseased cartilage orcartilage loss is measured 100. This step can be repeated multiple times101, as desired. Once the size of the cartilage defect is measured, thethickness of adjacent cartilage can optionally be measured 110. Thisprocess can also be repeated as desired 111. Either after measuring thecartilage loss or measuring the thickness of adjacent cartilage, thecurvature of the articular surface is then measured 120. Alternatively,the subchondral bone can be measured. Measurements may also be taken ofthe surface of the joint being repaired, or of the mating surface inorder to facilitate development of the best design for the implantsurface.

Once the surfaces have been measured, the user either selects the bestfitting implant contained in a library of implants 130, or generates apatient-specific implant 132. These steps can be repeated as desired ornecessary, 131, 133, to achieve the best-fitting implant for a patient.As will be appreciated, the process of selecting or designing an implantcan be tested against the information contained in the MRI or x-ray ofthe patient to ensure that the surfaces of the device achieve a good fitrelative to the patient's joint surface. Testing can be accomplished by,for example, superimposing the implant image over the image for thepatient's joint. Once it has been determined that a suitable implant hasbeen selected or designed, the implant site can be prepared 140, forexample by removing cartilage or bone from the joint surface, or theimplant can be placed into the joint 150.

The joint implant selected or designed achieves anatomic ornear-anatomic fit with the existing surface of the joint whilepresenting a mating surface for the opposing joint surface thatreplicates the natural joint anatomy. In this instance, both theexisting surface of the joint can be assessed as well as the desiredresulting surface of the joint. This technique is particularly usefulfor implants that are not anchored into the bone.

As will be appreciated, a physician, or other person, can obtain ameasurement of a target joint 10 and then either design 52 or select 50a suitable joint replacement implant.

II. Repair Materials

A wide variety of materials find use in the practice, including, but notlimited to, plastics, metals, crystal free metals, ceramics, biologicalmaterials (e.g., collagen or other extracellular matrix materials),hydroxyapatite, cells (e.g., stem cells, chondrocyte cells or the like),or combinations thereof. Based on the information (e.g., measurements)obtained regarding the defect and the articular surface and/or thesubchondral bone, a repair material can be formed or selected. Further,using one or more of these techniques described herein, a cartilagereplacement or regenerating material having a curvature that will fitinto a particular cartilage defect, will follow the contour and shape ofthe articular surface, and will match the thickness of the surroundingcartilage. The repair material can include any combination of materials,and typically includes at least one non-pliable material, for examplematerials that are not easily bent or changed.

A. Metal and Polymeric Repair Materials

Currently, joint repair systems often employ metal and/or polymericmaterials including, for example, prostheses which are anchored into theunderlying bone (e.g., a femur in the case of a knee prosthesis). See,e.g., U.S. Pat. Nos. 6,203,576 and 6,322,588, and references citedtherein. A wide-variety of metals are useful in the practice, and can beselected based on any criteria. For example, material selection can bebased on resiliency to impart a desired degree of rigidity. Non-limitingexamples of suitable metals include silver, gold, platinum, palladium,iridium, copper, tin, lead, antimony, bismuth, zinc, titanium, cobalt,stainless steel, nickel, iron alloys, cobalt alloys, such as Elgiloy®, acobalt-chromium-nickel alloy, and MP35N, anickel-cobalt-chromium-molybdenum alloy, and Nitinol™, a nickel-titaniumalloy, aluminum, manganese, iron, tantalum, crystal free metals, such asLiquidmetal® alloys (available from Liquid Metal Technologies,www.liquidmetal.com), other metals that can slowly form polyvalent metalions, for example to inhibit calcification of implanted substrates incontact with a patient's bodily fluids or tissues, and combinationsthereof.

Suitable synthetic polymers include polyamides (e.g., nylon),polyesters, polystyrenes, polyacrylates, vinyl polymers (e.g.,polyethylene, polytetrafluoroethylene, polypropylene and polyvinylchloride), polycarbonates, polyurethanes, poly dimethyl siloxanes,cellulose acetates, polymethyl methacrylates, polyether ether ketones,ethylene vinyl acetates, polysulfones, nitrocelluloses, similarcopolymers and mixtures thereof. Bioresorbable synthetic polymers canalso be used, such as dextran, hydroxyethyl starch, derivatives ofgelatin, polyvinylpyrrolidone, polyvinyl alcohol,poly[N-(2-hydroxypropyl-) methacrylamide], poly(hydroxy acids),poly(epsilon-caprolactone), polylactic acid, polyglycolic acid,poly(dimethyl glycolic acid), poly(hydroxy butyrate), and similarcopolymers can also be used.

Other appropriate materials include polyetheretherketone (PEEK™), e.g.,PEEK 450G, which is an unfilled PEEK approved for medical implantationavailable from Victrex (Lancashire, Great Britain, www.matweb.com),Boedeker www.boedeker.com) or Gharda (Panoli, India,www.ghardapolymers.com). The selected material may also be filled. Forexample, other grades of PEEK are also available, such as 30%glass-filled or 30% carbon filled, provided such materials are clearedfor use in implantable devices by the FDA, or other regulatory bodies.Glass filled PEEK reduces the expansion rate and increases the flexuralmodulus of PEEK relative to that portion which is unfilled. Theresulting product is known to be ideal for improved strength, stiffness,or stability. Carbon filled PEEK is known to enhance the compressivestrength and stiffness of PEEK and lower its expansion rate. Carbonfilled PEEK offers wear resistance and load carrying capability.

Other suitable biocompatible thermoplastic or thermoplasticpolycondensate materials that resist fatigue, have good memory, areflexible, and/or deflectable have very low moisture absorption, and goodwear and/or abrasion resistance, can be used. The implant can also becomprised of other polyketones, e.g., polyetherketoneketone (PEKK),polyetherketone (PEK), polyetherketoneetherketoneketone (PEKEKK),polyetheretherketoneketone (PEEKK), and polyaryletheretherketones. Othersuitable polymers include those described in WO 02/02158 A1, WO 02/00275A1, and WO 02/00270 A1.

Polymers can be prepared by a variety of approaches, includingconventional polymer processing methods. Exemplary approaches includeinjection molding, which is suitable for the production of polymercomponents with significant structural features; and rapid prototyping,such as reaction injection molding and stereo-lithography. The substratecan be textured or made porous by either physical abrasion or chemicalalteration to facilitate incorporation of the metal coating. Othersuitable processes include extrusion, injection, compression moldingand/or machining techniques. Typically, the polymer is chosen for itsphysical and mechanical properties and is suitable for carrying andspreading the physical load between the joint surfaces.

More than one metal and/or polymer can be used in combination with eachother. For example, one or more metal-containing substrates can becoated with polymers in one or more regions or, alternatively, one ormore polymer-containing substrate can be coated in one or more regionswith one or more metals.

The system or prosthesis can be porous or porous-coated. The poroussurface components can be made of various materials including metals,ceramics, and polymers. These surface components can, in turn, besecured by various means to a multitude of structural cores formed ofvarious metals. Suitable porous coatings include metal, ceramic,polymeric (e.g., biologically neutral elastomers such as siliconerubber, polyethylene terephthalate and/or combinations thereof orcombinations thereof. See, e.g., U.S. Pat. Nos. 3,605,123, 3,808,606,3,843,975, 3,314,420, 3,987,499 and German Offenlegungsschrift2,306,552. There can be more than one coating layer, and the layers canhave the same or different porosities. See, e.g., U.S. Pat. No.3,938,198.

The coating can be applied by surrounding a core with powdered polymerand heating until cured to form a coating with an internal network ofinterconnected pores. The tortuosity of the pores (e.g., a measure oflength to diameter of the paths through the pores) can be important inevaluating the probable success of such a coating in use on a prostheticdevice. See also U.S. Pat. No. 4,213,816. The porous coating can beapplied in the form of a powder and the article as a whole subjected toan elevated temperature that bonds the powder to the substrate.Selection of suitable polymers and/or powder coatings can be determinedin view of the teachings and references cited herein, for example, basedon the melt index of each.

Depending on a wear pattern analysis, it may be advantageous to utilizediffering materials or material composition (e.g., varying degrees ofpolymeric cross linking, or of metal/alloy hardness) in the implant bodyto address and correct the wear pattern. Variations in materialcomposition throughout the implant body can include the use of differentmaterials, e.g., different metals, plastics or ceramics, or theselection of one or more of these materials in, or adjacent to, theregion of the implant corresponding to a wear pattern. As noted above,select changes in material properties of the same material can be used;or, when a polymeric material is employed, selective cross-linking canbe performed in an area of or adjacent to a wear pattern to selectivelyvary the physical properties of the polymer. Selective cross-linking canbe achieved, for example with a radiation beam focused on, or adjacentto, the area of the device corresponding to the wear pattern, or by useof selective chemical cross linking.

A wear pattern analysis may include reviewing or analyzing a bonesurface to determine the presence of wear pattern indicia. The review oranalysis may be determined preoperatively (e.g., via imaging analysis)or intraoperatively, e.g., via arthroscopy, arthrotomic examination, orgait analysis. Linear or non-linear weightings can be applied; andmathematical and statistical modeling can be used to derive a wearpattern from the wear pattern indicia. Other parameters can beconsidered in determining a wear pattern, including the presence andseverity of ligament tears, muscle strength, body mass index,anthropometric parameters, and the estimated or measured location ofligaments, e.g., medial or lateral collateral ligaments, ACL and PCL,ligamentum capitis femoris, transverse ligaments, rotator cuff, andspinous ligaments.

Further considerations in designing the implant body to address andcorrect the wear pattern include decreasing or increasing materialthickness in response to the wear pattern (e.g., part of designing acharacteristic topography); change in implant shape, e.g., change inconvexity or concavity of one or more surfaces in one or moredimensions; enhanced matching of shape between two mating articularsurfaces (enhanced constraint); or decreased matching of shape betweentwo mating articular surfaces (decreased constraint). A characteristictopography may include the relief features of the superior surface, butalso variations in thickness of the device from region to region(elevation, in topographic terms.) In an embodiment, an implant can bedesigned or selected that is adapted or optimized for a patient's wearpattern or areas adjacent to a wear pattern, such adaptations oroptimizations resulting in an implant having a characteristictopography.

B. Biological Repair Materials

Repair materials can also include one or more biological material eitheralone or in combination with non-biological materials. For example, anybase material can be designed or shaped and suitable cartilagereplacement or regenerating material(s) such as fetal cartilage cellscan be applied to be the base. The cells can be then be grown inconjunction with the base until the thickness (and/or curvature) of thecartilage surrounding the cartilage defect has been reached. Conditionsfor growing cells (e.g., chondrocytes) on various substrates in culture,ex vivo and in vivo are described, for example, in U.S. Pat. Nos.5,478,739, 5,842,477, 6,283,980, and 6,365,405. Non-limiting examples ofsuitable substrates include plastic, tissue scaffold, a bone replacementmaterial (e.g., a hydroxyapatite, a bioresorbable material), or anyother material suitable for growing a cartilage replacement orregenerating material on it.

Biological polymers can be naturally occurring or produced in vitro,e.g., via fermentation. Suitable biological polymers include collagen,elastin, silk, keratin, gelatin, polyamino acids, cat gut sutures,polysaccharides (e.g., cellulose and starch) and mixtures thereof.Biological polymers can be bioresorbable. Biological materials can beautografts (from the same subject); allografts (from another individualof the same species) and/or xenografts (from another species). See alsoWO 02/22014 and WO 97/27885. In certain embodiments autologous materialsare preferred, as they can carry a reduced risk of immunologicalcomplications to the host, including re-absorption of the materials,inflammation and/or scarring of the tissues surrounding the implantsite.

Any biological repair material can be sterilized to inactivatebiological contaminants such as bacteria, viruses, yeasts, molds,mycoplasmas and parasites. Sterilization can be performed using anysuitable technique such as radiation, e.g., gamma radiation.

Any of the biological materials described herein can be harvested withuse of a robotic device. The robotic device can use information from anelectronic image for tissue harvesting.

III. Device Design

A. Cartilage Models

Using information on thickness and curvature of the cartilage, aphysical model of the surfaces of the articular cartilage and of theunderlying bone can be created. This physical model can berepresentative of a limited area within the joint or it can encompassthe entire joint. This model can also take into consideration thepresence or absence of a meniscus as well as the presence or absence ofsome or all of the cartilage. For example, in the knee joint, thephysical model can encompass only the medial or lateral femoral condyle,both femoral condyles and the notch region, the medial tibial plateau,the lateral tibial plateau, the entire tibial plateau, the medialpatella, the lateral patella, the entire patella or the entire joint.The location of a diseased area of cartilage can be determined, forexample using a 3D coordinate system or a 3D Euclidian distance asdescribed in WO 02/22014.

In this way, the size of the defect to be repaired can be determined.This process takes into account that, for example, roughly 80% ofpatients have a healthy lateral component. As will be apparent, some,but not all, defects will include less than the entire cartilage. Thus,in one embodiment, the thickness of the normal or only mildly diseasedcartilage surrounding one or more cartilage defects is measured. Thisthickness measurement can be obtained at a single point or, preferably,at multiple points, for example 2 point, 4-6 points, 7-10 points, morethan 10 points or over the length of the entire remaining cartilage.Furthermore, once the size of the defect is determined, an appropriatetherapy (e.g., articular repair system) can be selected such that asmuch as possible of the healthy, surrounding tissue is preserved.

In other embodiments, the curvature of the articular surface can bemeasured to design and/or shape the repair material. Further, both thethickness of the remaining cartilage and the curvature of the articularsurface can be measured to design and/or shape the repair material.Alternatively, the curvature of the subchondral bone can be measured andthe resultant measurement(s) can be used to either select or shape acartilage replacement material. For example, the contour of thesubchondral bone can be used to re-create a virtual cartilage surface:the margins of an area of diseased cartilage can be identified. Thesubchondral bone shape in the diseased areas can be measured. A virtualcontour can then be created by copying the subchondral bone surface intothe cartilage surface, whereby the copy of the subchondral bone surfaceconnects the margins of the area of diseased cartilage. In shaping thedevice, the contours can be configured to mate with existing cartilageor to account for the removal of some or all of the cartilage.

FIG. 2A shows a slightly perspective top view of a joint implant 200suitable for implantation at the tibial plateau of the knee joint. Asshown in FIG. 2A, the implant can be generated using, for example, adual surface assessment, as described above with respect to FIGS. 1A andB.

The implant 200 has an upper surface 202, a lower surface 204 and aperipheral edge 206. The upper surface 202 is formed so that it forms amating surface for receiving the opposing joint surface; in thisinstance partially concave to receive the femur. The concave surface canbe variably concave such that it presents a surface to the opposingjoint surface, e.g., a negative surface of the mating surface of thefemur it communicates with. As will be appreciated, the negativeimpression need not be a perfect one.

The upper surface 202 of the implant 200 can be shaped by a variety ofmeans. For example, the upper surface 202 can be shaped by projectingthe surface from the existing cartilage and/or bone surfaces on thetibial plateau, or it can be shaped to mirror the femoral condyle inorder to optimize the complimentary surface of the implant when itengages the femoral condyle. Alternatively, the superior surface 202(e.g., the outer surface of the implant, i.e., that which will interfacewith the opposing joint surface, or an implant affixed to the opposingjoint surface) can be configured to mate with an inferior surface (e.g.,the surface of the implant body that faces the articular surface towhich the implant is to be affixed) of an implant configured for theopposing femoral condyle.

The lower surface 204 has a convex surface that matches, or nearlymatches, the tibial plateau of the joint such that it creates ananatomic or near anatomic fit with the tibial plateau. Depending on theshape of the tibial plateau, the lower surface can be partially convexas well. Thus, the lower surface 204 presents a surface to the tibialplateau that fits within the existing surface. It can be formed to matchthe existing surface or to match the surface after articularresurfacing.

As will be appreciated, the convex surface of the lower surface 204 neednot be perfectly convex. Rather, the lower surface 204 is more likelyconsist of convex and concave portions that fit within the existingsurface of the tibial plateau or the re-surfaced plateau. Thus, thesurface is essentially variably convex and concave.

FIG. 2B shows a top view of the joint implant of FIG. 2A. As shown inFIG. 2B the exterior shape 208 of the implant can be elongated. Theelongated form can take a variety of shapes including elliptical,quasi-elliptical, race-track, etc. However, as will be appreciated theexterior dimension is typically irregular thus not forming a truegeometric shape, e.g., elliptical. As will be appreciated, the actualexterior shape of an implant can vary depending on the nature of thejoint defect to be corrected. Thus the ratio of the length L to thewidth W can vary from, for example, between 0.25 and 2.0, and moreparticularly from 0.5 to 1.5. As further shown in FIG. 2B, the lengthacross an axis of the implant 200 varies when taken at points along thewidth of the implant. For example, as shown in FIG. 2B, L₁≠L₂≠L₃.

Turning now to FIGS. 2C-E, cross-sections of the implant shown in FIG.2B are depicted along the lines of C--C, D-D, and E-E. The implant has athickness t1, t2 and t3 respectively. As illustrated by thecross-sections, the thickness of the implant varies along both itslength L and width W. The actual thickness at a particular location ofthe implant 200 is a function of the thickness of the cartilage and/orbone to be replaced and the joint mating surface to be replicated.Further, the profile of the implant 200 at any location along its lengthL or width W is a function of the cartilage and/or bone to be replaced.

FIG. 2F is a lateral view of the implant 200 of FIG. 2A. In thisinstance, the height of the implant 200 at a first end h₁ is differentthan the height of the implant at a second end h₂. Further the upperedge 208 can have an overall slope in a downward direction. However, asillustrated the actual slope of the upper edge 208 varies along itslength and can, in some instances, be a positive slope. Further thelower edge 210 can have an overall slope in a downward direction. Asillustrated the actual slope of the lower edge 210 varies along itslength and can, in some instances, be a positive slope. As will beappreciated, depending on the anatomy of an individual patient, animplant can be created wherein h₁ and h₂ are equivalent or substantiallyequivalent without departing from the scope.

FIG. 2G is a cross-section taken along a sagittal plane in a bodyshowing the implant 200 implanted within a knee joint 1020 such that thelower surface 204 of the implant 200 lies on the tibial plateau 1022 andthe femur 1024 rests on the upper surface 202 of the implant 200. FIG.2H is a cross-section taken along a coronal plane in a body showing theimplant 200 implanted within a knee joint 1020. As is apparent from thisview, the implant 200 is positioned so that it fits within a superiorarticular surface 224. As will be appreciated, the articular surface maybe the medial or lateral facet, as needed.

FIG. 2I is a view along an axial plane of the body showing the implant200 implanted within a knee joint 1020 showing the view taken from anaerial, or upper, view. FIG. 2J is a view of an alternate embodimentwhere the implant is a bit larger such that it extends closer to thebone medially, i.e., towards the edge 1023 of the tibial plateau, aswell as extending anteriorly and posteriorly.

FIG. 2K is a cross-section of an implant 200 according to an alternateembodiment. In this embodiment, the lower surface 204 further includes ajoint anchor 212. As illustrated in this embodiment, the joint anchor212 forms a protrusion, keel or vertical member that extends from thelower surface 204 of the implant 200 and projects into, for example, thebone of the joint. As will be appreciated, the keel can be perpendicularor lie within a plane of the body.

Additionally, as shown in FIG. 2L the joint anchor 212 can have across-member 214 so that from a bottom perspective, the joint anchor 212has the appearance of a cross or an “x.” As will be appreciated, thejoint anchor 212 may take on a variety of other forms while stillaccomplishing the same objective of providing increased stability of theimplant 200 in the joint. These forms include, but are not limited to,pins, bulbs, balls, teeth, etc. Additionally, one or more joint anchors212 can be provided as desired. FIGS. 2M and N illustrate cross-sectionsof alternate embodiments of a dual component implant from a side viewand a front view.

In an alternate embodiment shown in FIG. 2M it may be desirable toprovide a one or more cross-members 220 on the lower surface 204 inorder to provide a bit of translation movement of the implant relativeto the surface of the femur, or femur implant. In that event, thecross-member can be formed integral to the surface of the implant or canbe one or more separate pieces that fit within a groove 222 on the lowersurface 204 of the implant 200. The groove can form a single channel asshown in FIG. 2N-1, or can have more than one channel as shown in FIG.2O-1. In either event, the cross-bar then fits within the channel asshown in FIGS. 2N-2 and 2O-2. The cross-bar members 220 can form a solidor hollow tube or pipe structure as shown in FIG. 2P. Where two, ormore, tubes 220 communicate to provide translation, a groove 221 can beprovided along the surface of one or both cross-members to interlock thetubes into a cross-bar member further stabilizing the motion of thecross-bar relative to the implant 200. As will be appreciated, thecross-bar member 220 can be formed integrally with the implant withoutdeparting from the scope.

As shown in FIGS. 2Q-R, it is anticipated that the surface of the tibialplateau will be prepared by forming channels thereon to receive thecross-bar members. Thus facilitating the ability of the implant to seatsecurely within the joint while still providing movement about an axiswhen the knee joint is in motion.

FIG. 2S(1-9) illustrate an alternate embodiment of implant 200. Asillustrated in FIG. 2S the edges are beveled to relax a sharp corner.FIG. 2S(1) illustrates an implant having a single fillet or bevel 230.The fillet is placed on the implant anterior to the posterior portion ofthe tibial spine. As shown in FIG. 2S(2) two fillets 230, 231 areprovided and used for the posterior chamfer. In FIG. 2S(3) a thirdfillet 234 is provided to create two cut surfaces for the posteriorchamfer.

Turning now to FIG. 2S(4) a tangent of the implant is deselected,leaving three posterior curves. FIG. 2S(5) shows the result of tangentpropagation. FIG. 2S(6) illustrates the effect on the design when thebottom curve is selected without tangent propagation. The result oftangent propagation and selection is shown in FIG. 2S(7). As can be seenin FIG. 2S(8-9) the resulting corner has a softer edge but sacrificesless than 0.5 mm of joint space. As will be appreciated, additionalcutting planes can be added without departing from the scope.

FIG. 2T illustrates an alternate embodiment of an implant 200 whereinthe surface of the tibial plateau 250 is altered to accommodate theimplant. As illustrated in FIG. 2T(1-2) the tibial plateau can bealtered for only half of the joint surface 251 or for the full surface252. As illustrate in FIG. 2T(3-4) the posterior-anterior surface can beflat 260 or graded 262. Grading can be either positive or negativerelative to the anterior surface. Grading can also be used with respectto the implants of FIG. 2T where the grading either lies within a planeor a body or is angled relative to a plane of the body. Additionally,attachment mechanisms can be provided to anchor the implant to thealtered surface. As shown in FIG. 2T(5-7) keels 264 can be provided. Thekeels 264 can either sit within a plane, e.g., sagittal or coronalplane, or not sit within a plane (as shown in FIG. 2T(7)). FIG. 2T(8)illustrates an implant which covers the entire tibial plateau. The uppersurface of these implants are designed to conform to the projected shapeof the joint as determined under the steps described with respect toFIG. 1, while the lower surface is designed to be flat, or substantiallyflat to correspond to the modified surface of the joint.

Turning now to FIGS. 3A-I, an implant suitable for providing an opposingjoint surface to the implant of FIG. 2A is shown. This implant correctsa defect on an inferior surface of the femur 1024 (e.g., the condyle ofthe femur that mates with the tibial plateau) and can be used alone,i.e., on the femur 1024, or in combination with another joint repairdevice. Formation of the surfaces of the devices can be achieved usingthe techniques described above with respect to the implant of FIG. 2.

FIG. 3A shows a perspective view of an implant 300 having a curvedmating surface 302 and convex joint abutting surface 304. The jointabutting surface 304 need not form an anatomic or near anatomic fit withthe femur in view of the anchors 306 provided to facilitate connectionof the implant to the bone. In this instance, the anchors 306 are shownas pegs having notched heads. The notches facilitate the anchoringprocess within the bone. However, pegs without notches can be used aswell as pegs with other configurations that facilitate the anchoringprocess or cruciate stems. Pegs and other portions of the implant can beporous-coated. The implant can be inserted without bone cement or withuse of bone cement. The implant can be designed to abut the subchondralbone, i.e., it can substantially follow the contour of the subchondralbone. This has the advantage that no bone needs to be removed other thanfor the placement of the peg holes thereby significantly preserving bonestock.

The anchors 306 may take on a variety of other forms, while stillaccomplishing the objective of providing increased stability of theimplant 300 in the joint. These forms include, but are not limited to,pins, bulbs, balls, teeth, etc. Additionally, one or more joint anchors306 can be provided as desired. As illustrated in FIG. 3, three pins areused to anchor the implant 300. However, more or fewer joint anchors,cruciate stems, or pins, can be used without departing from the scope.

FIG. 3B shows a slightly perspective superior view of the bone matingsurface 304 further illustrating the use of three anchors 306 to anchorthe implant to the bone. Each anchor 306 has a stem 310 with a head 312on top. As shown in FIG. 3C, the stem 310 has parallel walls such thatit forms a tube or cylinder that extends from the bone mating surface304. A section of the stem forms a narrowed neck 314 proximal to thehead 312. As will be appreciated, the walls need not be parallel, butrather can be sloped to be shaped like a cone. Additionally, the neck314 need not be present, or the head 312. As discussed above, otherconfigurations suitable for anchoring can be used without departing fromthe scope.

Turning now to FIG. 3D, a view of the tibial plateau mating surface 302of the implant 300 is illustrated. As is apparent from this view, thesurface is curved such that it is convex or substantially convex inorder to mate with the concave surface of the plateau. FIG. 3Eillustrates the upper surface 304 of the implant 300 furtherillustrating the use of three pegs 306 for anchoring the implant 300 tothe bone. As illustrated, the three pegs 306 are positioned to form atriangle. However, as will be appreciated, one or more pegs can be used,and the orientation of the pegs 306 to one another can be as shown orany other suitable orientation that enables the desired anchoring. FIG.3F illustrated a cross section of the implant 300 taken along the linesF-F shown in FIG. 3E. Typically the pegs are oriented on the surface ofthe implant so that the peg is perpendicular to the femoral condyle,which may not result in the peg being perpendicular to the surface ofthe implant.

FIG. 3G illustrates the axial view of the femur 1000 having a lateralcondyle 1002 and a medial condyle 1004. The intercondylar fossa is alsoshown 1006 along with the lateral epicondyle 1008 and medial epicondyle1010. Also shown is the patellar surface of the femur 1012. The implant300 illustrated in FIG. 3A, is illustrated covering a portion of thelateral condyle. The pegs 306 are also shown that facilitate anchoringthe implant 300 to the condyle.

FIG. 3H illustrates a knee joint 1020 from an anterior perspective. Theimplant 300 is implanted over a condyle. As shown in FIG. 3I, theimplant 300 is positioned such that it communicates with an implant 200designed to correct a defect in the tibial plateau, such as those shownin FIG. 2.

FIGS. 3J-K illustrate an implant 300 for placement on a condyle. In thisembodiment, at least one flat surface or chamfer cut 360 is provided tomate with a cut made on the surface of the condyle in preparing thejoint. The flat surface 360 typically does not encompass the entireproximal surface 304 of the implant 300.

FIG. 4A illustrates the design of a typical total knee arthroplasty(“TKA”) primary knee 499. Posterior cuts 498, anterior cuts 497 anddistal cuts 496 are provided as well as chamfer cuts 495.

FIGS. 4B and 4C illustrate another implant 400. As shown in FIG. 4B, theimplant 400 is configured such that it covers both the lateral andmedial femoral condyle, along with the patellar surface of the femur1012. The implant 400 has a lateral condyle component 410 and a medialcondyle component 420 and a bridge 430 that connects the lateral condylecomponent 410 to the medial condyle component 420 while covering atleast a portion of the patellar surface of the femur 1012. The implant400 can optionally oppose one or more implants, such as those shown inFIG. 2, if desired. FIG. 4C is a side view of the implant of FIG. 4B. Asshown in FIG. 4C, the superior surface 402 of the implant 400 is curvedto correspond to the curvature of the femoral condyles. The curvaturecan be configured such that it corresponds to the actual curvature ofone or both of the existing femoral condyles, or to the curvature of oneor both of the femoral condyles after resurfacing of the joint. One ormore pegs 430 can be provided to assist in anchoring the implant to thebone. As will be appreciated, the implant can be configured such thatthe superior surface contacting a first condyle is configured to malewith the existing condyle while a surface contacting a second condylehas one or more flat surfaces to mate with a condyle surface that hasbeen modified.

FIG. 4D illustrates a top view of the implant 400 shown in FIG. 4B. Asshould be appreciated from this view, the inferior surface 404 of theimplant 400 is configured to conform to the shape of the femoralcondyles, e.g., the shape healthy femoral condyles would present to thetibial surface in a non-damaged joint.

FIGS. 4E and F illustrate perspective views of the implant from theinferior surface (i.e., tibial plateau mating surface).

FIG. 4G illustrates the axial view of the femur 1000 having a lateralcondyle 1002 and a medial condyle 1004. The intercondylar fossa is alsoshown 1006 along with the lateral epicondyle 1008. The implant 400illustrated in FIG. 4B is illustrated covering both condyles and thepatellar surface of the femur 1012. The pegs 430 are also shown thatfacilitate anchoring the implant 400 to the condyle.

FIG. 4H illustrates a knee joint 1050 from an anterior perspective. Theimplant 400 is implanted over both condyles. As shown in FIG. 4I, theimplant 400 is positioned such that it communicates with an implant 200designed to correct a defect in the tibial plateau, such as those shownin FIG. 2.

As will be appreciated, the implant 400 can be manufactured from amaterial that has memory such that the implant can be configured tosnap-fit over the condyle. Alternatively, it can be shaped such that itconforms to the surface without the need of a snap-fit.

FIGS. 5A and 5B illustrate yet another implant 500 suitable forrepairing a damaged condyle. As shown in FIG. 5A, the implant 500 isconfigured such that it covers only one of the lateral or medial femoralcondyles 510. The implant differs from the implant of FIG. 3 in that theimplant 500 also covers at least a portion of the patellar surface ofthe femur 512.

Similar to the implant of FIG. 4, the implant can optionally oppose oneor more implants or opposing joint surfaces, such as those shown in FIG.2, and can be combined with other implants, such as the implants of FIG.3. FIG. 5C is a perspective side view of the implant of FIG. 5A. Asshown in FIG. 5C, the superior surface 502 of the implant 500 is curvedto correspond to the curvature of the femoral condyle that it mates withand the portion of the patellar surface of the femur that it covers. Oneor more pegs 530 can be provided to assist in anchoring the implant tothe bone. Additionally, an angled surface 503 can be provided on aninterior surface 502 of the condyle component that conforms to anoptionally provided cut made on the surface of the joint surface withwhich the implant mates.

FIG. 5D illustrates a perspective top view of the implant 500 shown inFIG. 5A. It may be appreciated from this view that the inferior surface504 of the implant 500 is configured to conform to the projected shapeof the femoral condyles, e.g., the shape healthy femoral condyles wouldpresent to the tibial surface in a non-damaged joint.

FIG. 5E is a view of the implant 500 showing a hatched three pointloading support area which extends from a top portion 513 to a line(plane 17) and from a line (plane 18) to a bottom portion 515. Alsoillustrated are the pegs 530 extending from the superior surface. FIG.5F illustrates the superior surface of the implant 500 with the pegs 530extending from the superior surface. FIG. 5F also illustrates thehatched cantilever loading support area, which extends from the line(plane 18) to the top portion 513 of the implant. The loading forces anddirections for each support condition are based on physiological loadencounters. Table 1 shows the Physiological Loadings taken from a studyby Seth Greenwald.

TABLE 1 Physiological Loadings¹ Set-up “1” “2” “3” Flexion Angle 0° 60°90° (degree) Normal Force N 2,900 3,263 3,625 (lbs.) (652) (733.5) (815)Normal Force Walking Stair Descent Stair Ascent Case (4.0 × BW*) (4.5 ×BW*) (5.0 × BW*) Body Weight (BW) taken as a 60 year old male, with 173cm height for an average body weight of 74 kg (163 lbs). ¹”TibialPlateau Surface Stress in TKA: A Factor Influencing Polymer FailureSeries III- Posterior Stabilized Designs,” Paul D. Postak, B.Sc.,Christine S. Heim, B.Sc., A. Seth Greenwald, D. Phil., OrthopaedicResearch Laboratories, The Mt. Sinai Medical Center, Cleveland, Ohio.Presented at the 62^(nd) Annual AAOS Meeting, 1995.

Using the implant 500 described in this application, the three pointloading will occur from set-up 1 (2900 N). To replicate a worst caseloading scenario, a 75/25 load distribution (75% of 2900 N=2175 N) canbe used. The loading will be concentrated on a 6 mm diameter circulararea located directly below and normal to the pad on the bearingsurface.

Turning to the cantilever loading shown in FIG. 5F, the loading willoccur from set-up 3, or 90°, at a 75/25 load distribution (75% of 3625N=2719 N). As with the above example, the loading will be concentratedon a 6 mm diameter circular area located at the center of theposterior-most portion of the medial condyle normal to the flat cutsurface of the posterior condyle.

FIGS. 5G and H illustrate alternate embodiments of the implant 500having a rail design that provides one or more rails 521 along medialand/or lateral sides of the implant 500. The rail 521 can be positionedso that it extends along a portion of the medial 517 and/or lateral 519sides before communicating with the angled surface 503. As will beappreciated, a single side rail 521 can also be provided.

FIG. 5I illustrates another embodiment of an implant 500 having a keeldesign. A keel 523 (or centrally formed rail) is provided on thesuperior surface of the implant. In this embodiment, the keel 523 islocated on the surface of the implant, but not at the sides. As will beappreciated, the keel can be centered, as shown, substantially centered,or located off-center. An angled surface 503 can be provided tocommunicate with a modified joint surface. Alternatively, where thejoint surface is worn or modified, the cut 503 may be configured to matewith the worn or modified surface.

FIG. 5J illustrates the axial view of the femur 1000 having a lateralcondyle 1002 and a medial condyle 1004. The intercondylar fossa is alsoshown 1006 along with the lateral epicondyle 1008 and the medialepicondyle 1010. The patellar surface of the femur 1012 is alsoillustrated. The implant 500, illustrated in FIG. 5A, is shown coveringthe lateral condyle and a portion of the patellar surface of the femur1012. The pegs 530 facilitate anchoring the implant 500 to the condyleand patellar surface.

FIG. 5K illustrates a knee joint 1020 from an anterior perspective. Theimplant 500 is implanted over the lateral condyle. FIG. 5L illustrates aknee joint 1020 with the implant 500 covering the medial condyle 1004.As illustrated in FIGS. 5K and L, the shape of the implant 500corresponding to the patella surface may take on a variety ofcurvatures.

Turning now to FIGS. 5M and N the implant 500 is positioned such that itcommunicates with an implant 200 designed to correct a defect in thetibial plateau, such as those shown in FIG. 2.

In another embodiment, the implant 500 has a superior surface 502 whichsubstantially conforms to the surface of the condyle but which has atone flat portion corresponding to an oblique cut on the bone as shown inFIG. 5O.

Turning now to FIG. 5P-Q, an implant 500 is shown from a side view witha 7° difference between the anterior and posterior cuts.

FIG. 5R-S illustrate an implant 500 having a contoured surface 560 formating with the joint surface and an anterior cut 561 and a posteriorcut 562. FIG. 5S shows the same implant 500 from a slightly differentangle. FIG. 5T illustrates another implant 500 having a contouredsurface 560 for mating with the joint surface and posterior cut 562, adistal cut 563, and a chamfer cut 564. In this embodiment no anteriorcut is provided. FIG. 5U illustrates the implant 500 of FIG. 5T from aside perspective. The cuts are typically less than the cut required fora TKA, i.e., typically less than 10 mm. The design of the cuts for thisimplant allow for a revision surgery to the knee, if required, at alater date.

FIGS. 6A-G illustrate the implant 500 of FIG. 5 with a graphicalrepresentation of the cross-sections 610, 620 from which a surface shapeof the implant is derived. FIG. 6A illustrates a top view of the implant500 sitting on top of the extracted surface shape 600. This view of theimplant 500 illustrates a notch 514 associated with the bridge sectionof the implant 512 which covers the patellar surface of the femur (orthe trochlear region) to provide a mating surface that approximates thecartilage surface. As will be appreciated, the shape of an implantdesigned for the medial condyle would not necessarily be a mirror imageof the implant designed for the lateral condyle because of differencesin anatomy. Thus, for example, the notch 514 would not be present in animplant designed for the medial condyle and the patellar surface of thefemur. Therefore, the implant can be designed to include all or part ofthe trochlear region, or to exclude it entirely.

FIG. 6B illustrates a bottom view of the implant 500 layered overanother derived surface shape 601. FIG. 6C is a bottom view showing theimplant 500 extending through the extracted surface shape 600 shown inFIG. 6A. FIG. 6D is a close-up view of FIG. 6C, showing the condylarwing of the implant covering the extracted surface 600. FIG. 6Eillustrates a top posterior view of the implant 500 positioned over thegraphical representation of the surface shape 600. FIG. 6F is ananterior view and FIG. 6G is a bottom-posterior view.

FIG. 7A-C illustrate an implant 700 for correcting a joint similar tothe implant 500 above. However, implant 700 consists of two components.The first component 710 engages a condyle of the femur, either medial orlateral depending on the design. The second component 720 engages thepatellar surface of the femur. As discussed with the previousembodiments, the surfaces of the implant 700 may be configured such thatthe distal surface 722 (e.g., the surface that faces the tibial plateau)is shaped based on a projection of the natural shape of the femurcompensating the design for valgus or varus deformities and/orflattening of the surface of the femur. Alternatively, the distalsurface can be shaped based on the shape of the tibial plateau toprovide a surface designed to optimally mate with the tibial plateau.The proximal surface 724 (e.g., the surface that engages the femoralcondyle) can be configured such that it mirrors the surface of the femurin either its damaged condition or its modified condition. Likewise, theproximal surface can have one or more flattened sections 726 that form,e.g., chamfer cuts. Additionally the surface can include mechanismsfacilitating attachment 728 to the femur, such as keels, teeth, cruciatestems, and the like. The medial facing portion of the condyle implanthas a tapered surface 730 while the lateral facing portion of thepatellar component also has a tapered surface such that each componentpresents tapered surfaces 730 to the other component.

By dividing the surfaces of the medial and lateral compartments intoindependent articulating surfaces, as shown in FIG. 7, the implantprovides improved fit of the conformal surfaces to the subchondral bone.Additionally, the lateral-anterior portion of the femur is shielded fromstress which could cause bone loss. Also, the smaller size of eachcomponent of the implant enables the implant to be placed within thejoint using a smaller incision. Finally, the wear of the patellarcomponent is improved.

FIGS. 8A-F illustrate a patella 800 with an implant 810. The implant 810can have one or more pegs, cruciate stems, or other anchoringmechanisms, if desired. As will be appreciated, other designs can bearrived at using the teachings of this disclosure. FIG. 8A illustrates aperspective view of an intact patella 800. FIG. 8B illustrates thepatella 800 wherein one surface of the patella 800 has been cut for forma smooth surface 802 to mate with an implant. FIG. 8C illustrates thepatella 800 with an implant 810 positioned on the smooth surface 802.The implant 810 has a plate structure 812 that abuts the smooth surfaceof the patella 802 and a dome 814 positioned on the plate 812 so thatthe dome is positioned in situ such that it will match the location ofthe patellar ridge. The implant 810 can be configured such that the edgeof the plate is offset 1 mm from the actual edge of the patella, asillustrated. As will be appreciated, the plate 812 and dome 814 can beformed as a single unit or formed from multiple components. FIG. 8D is aside view of the implant 810 positioned on the patella 800. As shown,the dome is positioned on the implant such that it is off-center.Optimal positioning of the dome will be determined by the position ofthe patellar ridge.

Turning now to FIGS. 8E-F, the implant 810 is shown superimposed on theunaltered patella 800 in order to illustrate that the position of thedome 814 of the implant corresponds to the location of the patellarridge.

FIGS. 8G-J illustrate an alternative design for the patellar implant.FIG. 8G illustrates the implant 850 in its beginning stages as a blankwith a flat inferior surface 852 having pegs 854 extending therefrom foranchoring to the patella. The articular or superior surface 860 has arounded dome 856, and a round plate section 858 that can be machined tomatch the bone cut. The articular surface 860 takes on the appearance ofa “hat” or sombrero, having a dome with a rim. The center of the dome856 is also the center of the bearing surface. The rim 858 is cut toconform to the needs of the particular patient. FIG. 8J illustrates animplant which has been formed from the blank shown in FIGS. 8G-I. FIG.8I shows a plurality of possible cut lines 862, 862′ for purposes ofillustration.

FIGS. 9A-C illustrate a lateral view of a knee 1020 with a combinationof implants. In FIG. 9A, an implant covering the condyle 900, isillustrated. Suitable implants can be, for example, those shown in FIGS.3-8, as will be appreciated the portion of the condyle covered anteriorto posterior can include the entire weight bearing surface, a portionthereof, or a surface greater than the weight bearing surface. Thus, forexample, the implant can be configured to terminate prior to the sulcusterminalis or after the sulcus terminalis (e.g., the groove on the femurthat coincides with the area where load bearing on the joint surfacestops). As shown in FIGS. 9A-B, a patellar implant 900 can also beprovided. FIG. 9C illustrates a knee having a condyle implant 900, apatellar implant 800 and an implant for the tibial plateau 200.

FIGS. 10A-D provide an alternate view of the coronal plane of a kneejoint with one or more implants described above implanted therein. FIG.10A illustrates a knee having a tibial implant 200 placed therein. FIG.10B illustrates a knee with a condyle implant 300 placed therein. Asdescribed above, a plurality of the implants taught herein can beprovided within a joint in order to restore joint movement. FIG. 10Cillustrates a knee joint having two implants therein. First, a tibialimplant 200 is provided on the tibial plateau and a second implant 300is provided on the facing condyle. The implants may be installed suchthat the implants present each other mating surfaces (as illustrated),or not. For example, where the tibial implant 200 is placed in themedial compartment of the knee and the condyle implant 300 is placed inthe lateral compartment. Other combinations are possible. Turning now toFIG. 10D, a tibial implant 200 is provided along with a bicompartmentalcondyle implant 500. As discussed above, these implants may or may notbe associated with the same compartment of the knee joint.

The arthroplasty system can be designed to reflect aspects of the tibialshape, femoral shape and/or patellar shape. Tibial shape and femoralshape can include cartilage, bone or both. Moreover, the shape of theimplant can also include portions or all components of other articularstructures such as the menisci. The menisci are compressible, inparticular during gait or loading. For this reason, the implant can bedesigned to incorporate aspects of the meniscal shape accounting forcompression of the menisci during loading or physical activities. Forexample, the undersurface 204 of the implant 200 can be designed tomatch the shape of the tibial plateau including cartilage or bone orboth. The superior surface 202 of the implant 200 can be a composite ofthe articular surface of the tibia (in particular in areas that are notcovered by menisci) and the meniscus. Thus, the outer aspects of thedevice can be a reflection of meniscal height. Accounting forcompression, this can be, for example, 20%, 40%, 60% or 80% ofuncompressed meniscal height.

Similarly the superior surface 304 of the implant 300 can be designed tomatch the shape of the femoral condyle including cartilage or bone orboth. The inferior surface 302 of the implant 300 can be a composite ofthe surface of the tibial plateau (in particular in areas that are notcovered by menisci) and the meniscus. Thus, at least a portion of theouter aspects of the device can be a reflection of meniscal height.Accounting for compression, this can be, for example, 20%, 40%, 60% or80% of uncompressed meniscal height. These same properties can beapplied to the implants shown in FIGS. 4-8, as well.

In some embodiments, the outer aspect of the device reflecting themeniscal shape can be made of another, preferably compressible material.If a compressible material is selected it is preferably designed tosubstantially match the compressibility and biomechanical behavior ofthe meniscus.

The height and shape of the menisci for any joint surface to be repairedcan be measured directly on an imaging test. If portions, or all, of themeniscus are torn, the meniscal height and shape can be derived frommeasurements of a contralateral joint or using measurements of otherarticular structures that can provide an estimate on meniscaldimensions.

In another embodiment, the superior face of the implants 300, 400 or 500can be shaped according to the femur. The shape can preferably bederived from the movement patterns of the femur relative to the tibialplateau thereby accounting for variations in femoral shape andtibiofemoral contact area as the femoral condyle flexes, extends,rotates, translates and glides on the tibia and menisci. The movementpatterns can be measured using any current or future test know in theart such as fluoroscopy, MRI, gait analysis and combinations thereof.

The arthroplasty can have two or more components, one essentially matingwith the tibial surface and the other substantially articulating withthe femoral component. The two components can have a flat opposingsurface. Alternatively, the opposing surface can be curved. Thecurvature can be a reflection of the tibial shape, the femoral shapeincluding during joint motion, and the meniscal shape and combinationsthereof.

Wear pattern can be adjusted in any joint and for any type ofreplacement or resurfacing device. For example, wear patterns in hips,knees, ankles, elbows, shoulders, and spines can be adjusted and/orcorrected. Similarly, various types of devices associated with repairsof such joints can be used. For example, a wear pattern in a knee can beadjusted and/or corrected in various types of knee devices, including,without limitation, interpositional devices, uni-compartmental andbi-compartmental resurfacing devices, total resurfacing devices andtotal knee replacement devices. In cases where multiple contact pointsor wear patterns are identified in a joint, for example, wear patternsassociated with both the medial and lateral femoral condyles in a totalknee resurfacing, both can be corrected or improved.

The wear patterns can be adjusted to improve or reduce wear on a newdevice, such as a hip replacement or a uni-compartmental resurfacingdevice, to, for example, reduce wear on the device and increase theexpected lifetime of the device. Additionally, wear patterns can beadjusted to improve the overall kinematics of the joint, for example, toalter the kinematics to an improved or even ideal case to improve thepatient's overall motion in the joint. For example, a device can bedesigned for a knee joint that functions in a manner that increases wearand degradation of the joint such that the device, when implanted,alters the motion of the joint to a more ideal case with reduced wearand improved functionality.

When an orthopedic device is implanted into a joint, the wear pattern onthe articular surface(s) can be altered and controlled. For example,when a unicompartmental knee resurfacing device is implanted in a knee,the wear pattern on the tibial articular surface between the tibia andfemur can be changed such that the tibial articular surface functionsdifferently after the implant is in place and the wear pattern at thearticular surface is changed when compared to the wear pattern prior tosurgery. Unlike existing off-the-shelf implants, which may change thewear pattern simply by virtue of introducing a new geometry into thejoint, the wear pattern is changed by design based on the existinggeometry and/or kinematics of a particular patient or set or class ofpatients. This allows the wear pattern to be controlled for thatindividual patient or for a class or set of patients that exhibitsimilar characteristic wear patterns, joint geometries and/or jointkinematics. Thus, for example, an improved wear pattern can be designedinto a particular orthopedic implant that is specific to a singlepatient's anatomy, or the wear pattern can be altered based one or moredesigns from a library of designs that can be applied to one or morepatients exhibiting a particular set of characteristics that meetpredefined rules or other analyses. Further, the design can be based, atleast in part, on the geometry of the joint, on the kinematics of thejoint or on a combination thereof.

FIG. 11 illustrates in cross-section an embodiment for the hip featuringa wear pattern correcting resurfacing implant 1113 for a femoral head1112 of femur 1111. Implant 1113 features an inner surface 1116 whichconforms, e.g., in a mirror image fashion, to the surface of femoralhead 1112. The outer surface of implant 1113 has a generally sphericalcurvature which matches that of acetabular component 1115 so as topermit a freedom of joint motion comparable to that of a normal hipjoint. Inner surface 1116 features a wear pattern correcting surface1114 that conforms to a wear pattern on femoral head 1112.

FIGS. 12 and 13 illustrate in cross sectional view a glenoid member 1220and 1320. FIGS. 12 and 13 are identical, save for the geometry of thebearing surface as discussed below.) Glenoid member 1220 includes anaffixation surface 1242 for affixing the glenoid member 1220 to thescapula 1210. An upper, or superior, affixation peg 1244 projects fromthe device and is integral with the glenoid member 1220. Peg 1244 fitsinto hole 1260. A lower, or inferior, affixation peg 1248 also projectsfrom the glenoid member 1220 and is oriented in an offset direction,relative to the superior affixation peg 1244. Peg 1248 fits into hole1262. The inferior affixation peg 1248 is integral with the glenoidmember 1220. Glenoid component 1212 may desirably be constructed in aone-piece member of synthetic polymeric material, e.g., ultra highmolecular weight polyethylene (UHMWPE). Cement mantle 1278 affixes theglenoid component 1212 in place in the scapula 1210.

Glenoid component 1212 includes a glenoid member 1220 extending in asuperior-inferior direction, that is, in upward and downward directions,between an upper, or superior, edge 1222, and a lower, or inferior, edge1224. An obverse, or lateral, face 1226 at the front of the glenoidmember 1220 has a concave contour configuration and provides bearingmeans in the form of a concave bearing surface 1228 for receiving ahumeral head. An aspect can be seen in FIG. 12, wherein the concavity ofbearing surface 1228 has been adjusted inferiorly to match an inferiorwear pattern on the humeral head. In FIG. 13, the concavity of bearingsurface 1228 has been adjusted superiorly to match a superior wearpattern on the humeral head.

FIGS. 14-16 illustrate, in simplified coronal view, a tibia with medial(FIG. 14), lateral (FIG. 15) and central (FIG. 16) lateral tibialplateau wear patterns, and a lateral tibial plateau implant featuring awear pattern correcting bearing surface for each respective type of wearpattern. Tibia 1414 includes lateral tibial plateau 1413, medial tibialplateau 1412, and tibial spine 1411. A medial wear pattern 1410 can beseen in the lateral tibial plateau 1413. Device 1415 is an implanthaving a bearing surface 1418 based on patient-specific information anddesirably derived from imaging data as described herein. In device 1415,the concavity of bearing surface 1418 is adjusted medially to accountfor, and adapt to, the wear characteristics of this particular patient.Device 1415 also features integral keel 1416 and pegs 1417 (which arebetter seen in FIGS. 17-19.)

In FIG. 15, a lateral wear pattern 1510 can be seen in the lateraltibial plateau 1513. Device 1515 is an implant having a bearing surface1518 based on patient-specific information and desirably derived fromimaging data as described herein. In device 1515, the concavity ofbearing surface 1518 is adjusted laterally to account for, and adapt to,the wear characteristics of this particular patient.

In FIG. 16, a central wear pattern 1610 can be seen in the lateraltibial plateau 1613. Device 1615 is an implant having a bearing surface1618 based on patient-specific information and desirably derived fromimaging data as described herein. In device 1615, the concavity ofbearing surface 1618 is adjusted centrally to account for, and adapt to,the wear characteristics of this particular patient.

FIGS. 17-19 illustrate, in simplified sagittal view, a tibia withposterior (FIG. 17), anterior (FIG. 18) and central (FIG. 19) lateraltibial plateau wear patterns, and a lateral tibial plateau implantfeaturing a wear pattern correcting bearing surface for each respectivetype of wear pattern. Tibia 1714 includes lateral tibial plateau 1713,and tibial spine 1711. A posterior wear pattern 1710 can be seen in thelateral tibial plateau 1713. Device 1715 is an implant having a bearingsurface 1718 based on patient-specific information and desirably derivedfrom imaging data as described herein. In device 1715, the concavity ofbearing surface 1718 is adjusted posteriorly to account for, and adaptto, the wear characteristics of this particular patient. Device 1715also features integral keel 1716 and pegs 1717.

In FIG. 18, an anterior wear pattern 1810 can be seen in the lateraltibial plateau 1813. Device 1815 is an implant having a bearing surface1818 based on patient-specific information and desirably derived fromimaging data as described herein. In device 1815, the concavity ofbearing surface 1818 is adjusted anteriorly to account for, and adaptto, the wear characteristics of this particular patient.

In FIG. 19, a central wear pattern 1910 can be seen in the lateraltibial plateau 1913. Device 1915 is an implant having a bearing surface1918 based on patient-specific information and desirably derived fromimaging data as described herein. In device 1915, the concavity ofbearing surface 1918 is adjusted centrally to account for, and adapt to,the wear characteristics of this particular patient.

In the above embodiments, if desirable, the width of the concavity,e.g., in the tibial and glenoid components, may be widened to provide aless constraining arrangement if the wear pattern is wide. Alternately,if desirable, the width of the concavity, e.g., in the tibial andglenoid components, may be narrowed to provide a more constrainingarrangement if wear pattern is narrow.

Various components and combinations of components can be used in devicesthat correct or adjust wear patters. Examples of single-componentsystems include plastics, polymers, metals, metal alloys, crystal freemetals, biologic materials, or combinations thereof. In certainembodiments, the surface of the repair system facing the underlying bonecan be smooth. In other embodiments, the surface of the repair systemfacing the underlying bone can be porous or porous-coated. In anotheraspect, the surface of the repair system facing the underlying bone isdesigned with one or more grooves, for example to facilitate thein-growth of the surrounding tissue. The external surface of the devicecan have a step-like design, which can be advantageous for alteringbiomechanical stresses. Optionally, flanges can also be added at one ormore positions on the device (e.g., to prevent the repair system fromrotating, to control toggle and/or prevent settling into the marrowcavity). The flanges can be part of a conical or a cylindrical design. Aportion or all of the repair system facing the underlying bone can alsobe flat which can help to control depth of the implant and to preventtoggle.

Examples of multiple-component systems include combinations of metals,plastics, metal alloys, crystal free metals, and biological materials.One or more components of the articular surface repair system can becomposed of a biologic material (e.g., a tissue scaffold with cells suchas cartilage cells or stem cells alone or seeded within a substrate suchas a bioresorbable material or a tissue scaffold, allograft, autograftor combinations thereof) and/or a non-biological material (e.g.,polyethylene or a chromium alloy such as chromium cobalt).

Thus, the repair system can include one or more areas of a singlematerial or a combination of materials, for example, the articularsurface repair system can have a first and a second component. The firstcomponent is typically designed to have size, thickness and curvaturesimilar to that of the cartilage tissue lost while the second componentis typically designed to have a curvature similar to the subchondralbone. In addition, the first component can have biomechanical propertiessimilar to articular cartilage, including but not limited to similarelasticity and resistance to axial loading or shear forces. The firstand the second component can consist of two different metals or metalalloys. One or more components of the system (e.g., the second portion)can be composed of a biologic material including bone or a non-biologicmaterial, e.g., hydroxyapatite, tantalum, chromium alloys, chromiumcobalt or other metal alloys.

One or more regions of the articular surface repair system (e.g., theouter margin of the first portion and/or the second portion) can bebioresorbable, for example to allow the interface between the articularsurface repair system and the patient's normal cartilage, over time, tobe filled in with hyaline or fibrocartilage. Similarly, one or moreregions (e.g., the outer margin of the first portion of the articularsurface repair system and/or the second portion) can be porous. Thedegree of porosity can change throughout the porous region, linearly ornon-linearly, for where the degree of porosity will typically decreasetowards the center of the articular surface repair system. The pores canbe designed for in-growth of cartilage cells, cartilage matrix, andconnective tissue thereby achieving a smooth interface between thearticular surface repair system and the surrounding cartilage.

The repair system (e.g., the second component in multiple componentsystems) can be attached to the patient's bone with use of a cement-likematerial such as methylmethacrylate, injectable hydroxy- orcalcium-apatite materials and the like.

In certain embodiments, one or more portions of the articular surfacerepair system can be pliable or liquid or deformable at the time ofimplantation and can harden later. Hardening can occur, for example,within 1 second to 2 hours (or any time period therebetween), preferablywith in 1 second to 30 minutes (or any time period therebetween), morepreferably between 1 second and 10 minutes (or any time periodtherebetween).

One or more components of the articular surface repair system can beadapted to receive injections. For example, the external surface of thearticular surface repair system can have one or more openings therein.The openings can be sized to receive screws, tubing, needles or otherdevices which can be inserted and advanced to the desired depth, forexample, through the articular surface repair system into the marrowspace. Injectables such as methylmethacrylate and injectable hydroxy- orcalcium-apatite materials can then be introduced through the opening (ortubing inserted therethrough) into the marrow space thereby bonding thearticular surface repair system with the marrow space. Similarly, screwsor pins, or other anchoring mechanisms can be inserted into the openingsand advanced to the underlying subchondral bone and the bone marrow orepiphysis to achieve fixation of the articular surface repair system tothe bone. Portions or all components of the screw or pin can bebioresorbable, for example, the distal portion of a screw that protrudesinto the marrow space can be bioresorbable. During the initial periodafter the surgery, the screw can provide the primary fixation of thearticular surface repair system. Subsequently, ingrowth of bone into aporous-coated area along the undersurface of the articular cartilagerepair system can take over as the primary stabilizer of the articularsurface repair system against the bone.

The articular surface repair system can be anchored to the patient'sbone with use of a pin or screw or other attachment mechanism. Theattachment mechanism can be bioresorbable. The screw or pin orattachment mechanism can be inserted and advanced towards the articularsurface repair system from a non-cartilage covered portion of the boneor from a non-weight-bearing surface of the joint.

The interface between the articular surface repair system and thesurrounding normal cartilage can be at an angle, for example oriented atan angle of 90 degrees relative to the underlying subchondral bone.Suitable angles can be determined in view of the teachings herein, andin certain cases, non-90 degree angles can have advantages with regardto load distribution along the interface between the articular surfacerepair system and the surrounding normal cartilage.

The interface between the articular surface repair system and thesurrounding normal cartilage and/or bone can be covered with apharmaceutical or bioactive agent, for example a material thatstimulates the biological integration of the repair system into thenormal cartilage and/or bone. The surface area of the interface can beirregular, for example, to increase exposure of the interface topharmaceutical or bioactive agents.

D. Pre-Existing Repair Systems

As described herein, repair systems of various sizes, curvatures andthicknesses can be obtained. These repair systems can be catalogued andstored to create a library of systems from which an appropriate systemfor an individual patient can then be selected. In other words, adefect, or an articular surface, is assessed in a particular subject anda pre-existing repair system having a suitable shape and size isselected from the library for further manipulation (e.g., shaping) andimplantation.

E. Mini-Prosthesis

The methods and compositions described herein can be used to replaceonly a portion of the articular surface, for example, an area ofdiseased cartilage or lost cartilage on the articular surface. In thesesystems, the articular surface repair system can be designed to replaceonly the area of diseased or lost cartilage or it can extend beyond thearea of diseased or lost cartilage, e.g., 3 or 5 mm into normal adjacentcartilage. In certain embodiments, the prosthesis replaces less thanabout 70% to 80% (or any value therebetween) of the articular surface(e.g., any given articular surface such as a single femoral condyle,etc.), preferably, less than about 50% to 70% (or any valuetherebetween), more preferably, less than about 30% to 50% (or any valuetherebetween), more preferably less than about 20% to 30% (or any valuetherebetween), even more preferably less than about 20% of the articularsurface.

The prosthesis can include multiple components, for example a componentthat is implanted into the bone (e.g., a metallic device) attached to acomponent that is shaped to cover the defect of the cartilage overlayingthe bone. Additional components, for example intermediate plates,meniscal repair systems and the like can also be included. It iscontemplated that each component replaces less than all of thecorresponding articular surface. However, each component need notreplace the same portion of the articular surface. In other words, theprosthesis can have a bone-implanted component that replaces less than30% of the bone and a cartilage component that replaces 60% of thecartilage. The prosthesis can include any combination, provided eachcomponent replaces less than the entire articular surface.

The articular surface repair system can be formed or selected so that itwill achieve a near anatomic fit or match with the surrounding oradjacent cartilage or bone. Typically, the articular surface repairsystem is formed and/or selected so that its outer margin located at theexternal surface will be aligned with the surrounding or adjacentcartilage.

Thus, the articular repair system can be designed to replace theweight-bearing portion (or more or less than the weight bearing portion)of an articular surface, for example in a femoral condyle. Theweight-bearing surface refers to the contact area between two opposingarticular surfaces during activities of normal daily living (e.g.,normal gait). At least one or more weight-bearing portions can bereplaced in this manner, e.g., on a femoral condyle and on a tibia.

In other embodiments, an area of diseased cartilage or cartilage losscan be identified in a weight-bearing area and only a portion of theweight-bearing area, specifically the portion containing the diseasedcartilage or area of cartilage loss, can be replaced with an articularsurface repair system.

In another embodiment, the articular repair system can be designed orselected to replace substantially the entire articular surface, e.g., acondyle.

In another embodiment, for example, in patients with diffuse cartilageloss, the articular repair system can be designed to replace an areaslightly larger than the weight-bearing surface.

In certain aspects, the defect to be repaired is located only on onearticular surface, typically the most diseased surface. For example, ina patient with severe cartilage loss in the medial femoral condyle butless severe disease in the tibia, the articular surface repair systemcan only be applied to the medial femoral condyle. Preferably, in anymethods described herein, the articular surface repair system isdesigned to achieve an exact or a near anatomic fit with the adjacentnormal cartilage.

In other embodiments, more than one articular surface can be repaired.The area(s) of repair will be typically limited to areas of diseasedcartilage or cartilage loss or areas slightly greater than the area ofdiseased cartilage or cartilage loss within the weight-bearingsurface(s).

In another embodiment, one or more components of the articular surfacerepair (e.g., the surface of the system that is pointing towards theunderlying bone or bone marrow) can be porous or porous-coated. Avariety of different porous metal coatings have been proposed forenhancing fixation of a metallic prosthesis by bone tissue in-growth.Thus, for example, U.S. Pat. No. 3,855,638, discloses a surgicalprosthetic device, which can be used as a bone prosthesis, comprising acomposite structure consisting of a solid metallic material substrateand a porous coating of the same solid metallic material adhered to andextending over at least a portion of the surface of the substrate. Theporous coating consists of a plurality of small discrete particles ofmetallic material bonded together at their points of contact with eachother to define a plurality of connected interstitial pores in thecoating. The size and spacing of the particles, which can be distributedin a plurality of monolayers, can be such that the average interstitialpore size is not more than about 200 microns. Additionally, the poresize distribution can be substantially uniform from thesubstrate-coating interface to the surface of the coating. In anotherembodiment, the articular surface repair system can contain one or morepolymeric materials that can be loaded with and release therapeuticagents including drugs or other pharmacological treatments that can beused for drug delivery. The polymeric materials can, for example, beplaced inside areas of porous coating. The polymeric materials can beused to release therapeutic drugs, e.g., bone or cartilage growthstimulating drugs. This embodiment can be combined with otherembodiments, wherein portions of the articular surface repair system canbe bioresorbable. For example, the first layer of an articular surfacerepair system or portions of its first layer can be bioresorbable. Asthe first layer gets increasingly resorbed, local release of a cartilagegrowth-stimulating drug can facilitate in-growth of cartilage cells andmatrix formation.

In any of the methods or compositions described herein, the articularsurface repair system can be pre-manufactured with a range of sizes,curvatures and thicknesses. Alternatively, the articular surface repairsystem can be custom-made for an individual patient.

IV. Manufacturing

A. Shaping

In certain instances shaping of the repair material will be requiredbefore or after formation (e.g., growth to desired thickness), forexample where the thickness of the required cartilage material is notuniform (e.g., where different sections of the cartilage replacement orregenerating material require different thicknesses).

The replacement material can be shaped by any suitable techniqueincluding, but not limited to, casting techniques, mechanical abrasion,laser abrasion or ablation, radiofrequency treatment, cryoablation,variations in exposure time and concentration of nutrients, enzymes orgrowth factors and any other means suitable for influencing or changingcartilage thickness. See, e.g., WO 00/15153. If enzymatic digestion isused, certain sections of the cartilage replacement or regeneratingmaterial can be exposed to higher doses of the enzyme or can be exposedlonger as a means of achieving different thicknesses and curvatures ofthe cartilage replacement or regenerating material in different sectionsof said material.

The material can be shaped manually and/or automatically, for exampleusing a device into which a pre-selected thickness and/or curvature hasbeen input and then programming the device using the input informationto achieve the desired shape.

In addition to, or instead of, shaping the cartilage repair material,the site of implantation (e.g., bone surface, any cartilage materialremaining, etc.) can also be shaped by any suitable technique in orderto enhance integration of the repair material.

B. Sizing

The articular repair system can be formed or selected so that it willachieve a near anatomic fit or match with the surrounding or adjacentcartilage, subchondral bone, menisci and/or other tissue. The shape ofthe repair system can be based on an imaging analysis. If the articularrepair system is intended to replace an area of diseased cartilage orlost cartilage, the near anatomic fit can be achieved using a methodthat provides a virtual reconstruction of the shape of healthy cartilagein an electronic image or reflect or conform to a wear pattern. Animaging analysis may include conventional and digital imaging techniquesknown in the art, including x-ray imaging and processing; fluoroscopy;digital tomosynthesis; ultrasound including A-scan, B-scan and C-scan;optical coherence, conventional, cone beam, or spiral computedtomography (CT); single photon emission tomography (SPECT); bone scan;positron emission tomography (PET); magnetic resonance imaging (MRI);thermal imaging; and optical imaging, or a combination thereof. Suchtechniques are explained fully in the literature and need not bedescribed herein. See, e.g., X-Ray Structure Determination: A PracticalGuide, 2nd Ed., Stout et al., eds. Wiley & Sons, 1989; Body CT: APractical Approach, Slone, ed., McGraw-Hill 1999; X-ray Diagnosis: APhysician's Approach, Lam, ed., Springer-Verlag 1998; Dental Radiology:Understanding the X-Ray Image, Brocklebank, ed., Oxford University Press1997; and The Essential Physics of Medical Imaging (2^(nd) Ed.),Bushberg et al.

In one embodiment, a near normal cartilage surface at the position ofthe cartilage defect can be reconstructed by interpolating the healthycartilage surface across the cartilage defect or area of diseasedcartilage. This can, for example, be achieved by describing the healthycartilage by means of a parametric surface (e.g., a B-spline surface),for which the control points are placed such that the parametric surfacefollows the contour of the healthy cartilage and bridges the cartilagedefect or area of diseased cartilage. The continuity properties of theparametric surface will provide a smooth integration of the part thatbridges the cartilage defect or area of diseased cartilage with thecontour of the surrounding healthy cartilage. The part of the parametricsurface over the area of the cartilage defect or area of diseasedcartilage can be used to determine the shape or part of the shape of thearticular repair system to match with the surrounding cartilage.

In another embodiment, a near normal cartilage surface at the positionof the cartilage defect or area of diseased cartilage can bereconstructed using morphological image processing. In a first step, thecartilage can be extracted from the electronic image using manual,semi-automated and/or automated segmentation techniques (e.g., manualtracing, region growing, live wire, model-based segmentation), resultingin a binary image. Defects in the cartilage appear as indentations thatcan be filled with a morphological closing operation performed in 2-D or3-D with an appropriately selected structuring element. The closingoperation is typically defined as a dilation followed by an erosion. Adilation operator sets the current pixel in the output image to 1 if atleast one pixel of the structuring element lies inside a region in thesource image. An erosion operator sets the current pixel in the outputimage to 1 if the whole structuring element lies inside a region in thesource image. The filling of the cartilage defect or area of diseasedcartilage creates a new surface over the area of the cartilage defect orarea of diseased cartilage that can be used to determine the shape orpart of the shape of the articular repair system to match with thesurrounding cartilage or subchondral bone.

As described above, the articular repair system can be formed orselected from a library or database of systems of various sizes,curvatures and thicknesses so that it will achieve a near anatomic fitor match with the surrounding or adjacent cartilage and/or subchondralbone. These systems can be pre-made or made to order for an individualpatient. In order to control the fit or match of the articular repairsystem with the surrounding or adjacent cartilage or subchondral bone ormenisci and other tissues preoperatively, a software program can be usedthat projects the articular repair system over the anatomic positionwhere it will be implanted. Suitable software is commercially availableand/or readily modified or designed by a skilled programmer.

In yet another embodiment, the articular surface repair system can beprojected over the implantation site using one or more 3-D images. Thecartilage and/or subchondral bone and other anatomic structures areextracted from a 3-D electronic image such as an MRI or a CT usingmanual, semi-automated and/or automated segmentation techniques. A 3-Drepresentation of the cartilage and/or subchondral bone and otheranatomic structures as well as the articular repair system is generated,for example using a polygon or NURBS surface or other parametric surfacerepresentation. For a description of various parametric surfacerepresentations see, for example Foley, J. D. et al., Computer Graphics:Principles and Practice in C; Addison-Wesley, 2^(nd) edition, 1995.

The 3-D representations of the cartilage and/or subchondral bone andother anatomic structures and the articular repair system can be mergedinto a common coordinate system. The articular repair system can then beplaced at the desired implantation site. The representations of thecartilage, subchondral bone, menisci and other anatomic structures andthe articular repair system are rendered into a 3-D image, for exampleapplication programming interfaces (APIs) OpenGL® (standard library ofadvanced 3-D graphics functions developed by SGI, Inc.; available aspart of the drivers for PC-based video cards, for example fromwww.nvidia.com for NVIDIA video cards orati.amd.com for ATI/AMDproducts) or DirectX® (multimedia API for Microsoft Windows® based PCsystems; available from www.microsoft.com). The 3-D image can berendered showing the cartilage, subchondral bone, menisci or otheranatomic objects, and the articular repair system from varying angles,e.g., by rotating or moving them interactively or non-interactively, inreal-time or non-real-time.

The software can be designed so that the articular repair system,including surgical tools and instruments with the best fit relative tothe cartilage and/or subchondral bone is automatically selected, forexample using some of the techniques described above. Alternatively, theoperator can select an articular repair system, including surgical toolsand instruments and project it or drag it onto the implantation siteusing suitable tools and techniques. The operator can move and rotatethe articular repair systems in three dimensions relative to theimplantation site and can perform a visual inspection of the fit betweenthe articular repair system and the implantation site. The visualinspection can be computer assisted. The procedure can be repeated untila satisfactory fit has been achieved. The procedure can be performedmanually by the operator; or it can be computer-assisted in whole orpart. For example, the software can select a first trial implant thatthe operator can test. The operator can evaluate the fit. The softwarecan be designed and used to highlight areas of poor alignment betweenthe implant and the surrounding cartilage or subchondral bone or meniscior other tissues. Based on this information, the software or theoperator can then select another implant and test its alignment. One ofskill in the art will readily be able to select, modify and/or createsuitable computer programs for the purposes described herein.

In another embodiment, the implantation site can be visualized using oneor more cross-sectional 2-D images. Typically, a series of 2-Dcross-sectional images will be used. The articular repair system canthen be superimposed onto one or more of these 2-D images. The 2-Dcross-sectional images can be reconstructed in other planes, e.g., fromsagittal to coronal, etc. Isotropic data sets (e.g., data sets where theslice thickness is the same or nearly the same as the in-planeresolution) or near isotropic data sets can also be used. Multipleplanes can be displayed simultaneously, for example using a split screendisplay. The operator can also scroll through the 2-D images in anydesired orientation in real time or near real time; the operator canrotate the imaged tissue volume while doing this. The articular repairsystem can be displayed in cross-section utilizing different displayplanes, e.g., sagittal, coronal or axial, typically matching those ofthe 2-D images demonstrating the cartilage, subchondral bone, menisci orother tissue. Alternatively, a three-dimensional display can be used forthe articular repair system. The 2-D electronic image and the 2-D or 3-Drepresentation of the articular repair system can be merged into acommon coordinate system. The articular repair system can then be placedat the desired implantation site. The series of 2-D cross-sections ofthe anatomic structures, the implantation site and the articular repairsystem can be displayed interactively (e.g., the operator can scrollthrough a series of slices) or non-interactively (e.g., as an animationthat moves through the series of slices), in real-time or non-real-time.

C. Rapid Prototyping

Rapid prototyping is a technique for fabricating a three-dimensionalobject from a computer model of the object. A special printer is used tofabricate the prototype from a plurality of two-dimensional layers.Computer software sections the representations of the object into aplurality of distinct two-dimensional layers and then athree-dimensional printer fabricates a layer of material for each layersectioned by the software. Together the various fabricated layers formthe desired prototype. More information about rapid prototypingtechniques is available in U.S. Publication No. 2002/0079601A1. Anadvantage to using rapid prototyping is that it enables the use of freeform fabrication techniques that use toxic or potent compounds safely.These compounds can be safely incorporated in an excipient envelope,which reduces worker exposure

A powder piston and build bed are provided. Powder includes any material(metal, plastic, etc.) that can be made into a powder or bonded with aliquid. The power is rolled from a feeder source with a spreader onto asurface of a bed. The thickness of the layer is controlled by thecomputer. The print head then deposits a binder fluid onto the powderlayer at a location where it is desired that the powder bind. Powder isagain rolled into the build bed and the process is repeated, with thebinding fluid deposition being controlled at each layer to correspond tothe three-dimensional location of the device formation. For a furtherdiscussion of this process see, e.g., U.S. Patent Publication No.2003/017365A1.

The rapid prototyping can use the two dimensional images obtained, asdescribed above, to determine each of the two-dimensional shapes foreach of the layers of the prototyping machine. In this scenario, eachtwo dimensional image slice would correspond to a two-dimensionalprototype slide. Alternatively, the three-dimensional shape of thedefect can be determined, as described above, and then broken down intotwo dimensional slices for the rapid prototyping process. The advantageof using the three-dimensional model is that the two-dimensional slicesused for the rapid prototyping machine can be along the same plane asthe two-dimensional images taken or along a different plane altogether.

Rapid prototyping can be combined or used in conjunction with castingtechniques. For example, a shell or container with inner dimensionscorresponding to an articular repair system can be made using rapidprototyping. Plastic or wax-like materials are typically used for thispurpose. The inside of the container can subsequently be coated, forexample with a ceramic, for subsequent casting. Using this process,personalized casts can be generated.

Rapid prototyping can be used for producing articular repair systems.Rapid prototyping can be performed at a manufacturing facility.Alternatively, it may be performed in the operating room after anintraoperative measurement has been performed.

Wear pattern-specific implant shapes or geometries can be achieved usinga number of different manufacturing techniques known in the art,including polishing, milling, machining, casting, rapid protocasting,laser sintering, laser melting and electro abrasion. In one embodiment,the wear pattern-adapted articular surface may be formed de novo. Inanother embodiment, the wear pattern-adapted articular surface may beformed by processing an implant with a standard shape of the articularsurface (a “blank”) and adapting the shape for the particular wearpattern, e.g., using machining or electroabrasion.

V. Surgical Techniques

Prior to performing surgery on a patient, the surgeon can preoperativelymake a determination of the alignment of the knee using, for example, anerect AP x-ray. In performing preoperative assessment any lateral andpatella spurs that are present can be identified.

Using standard surgical techniques, the patient is anesthetized and anincision is made in order to provide access to the portion or portionsof the knee joint to be repaired. A medial portal can be used initiallyto enable arthroscopy of the joint. Thereafter, the medial portal can beincorporated into the operative incision and/or standard lateral portalscan be used.

Once an appropriate incision has been made, the exposed compartment isinspected for integrity, including the integrity of the ligamentstructures. If necessary, portions of the meniscus can be removed aswell as any spurs or osteophytes that were identified in the AP x-ray orthat may be present within the joint. In order to facilitate removal ofosteophytes, the surgeon may flex the knee to gain exposure toadditional medial and medial-posterior osteophytes. Additionally,osteophytes can be removed from the patella during this process. Ifnecessary, the medial and/or lateral meniscus can also be removed atthis point, if desired, along with the rim of the meniscus.

As would be appreciated by those of skill in the art, evaluation of themedial cruciate ligament may be required to facilitate tibial osteophyteremoval.

Once the joint surfaces have been prepared, the desired implants can beinserted into the joint.

A. Tibial Plateau

To insert the device 200 of FIG. 2 into the medial compartment, amini-incision arthrotomy medial to the patella tendon is made. Once theincision is made, the medial condyle is exposed and a medial sleeve isprepared to about 1 cm below the joint line using a suitable knife andcurved osteotome. After preparing the medial sleeve, a Z-retractor isplaced around the medial tibial plateau and anterior portions of themeniscus and the osteophytes along the tibia and femur are removed. Atthis point, the knee should be flexed to about 60° or more. TheZ-retractor is removed and the implant is placed against the most distalaspect of the femur and over the tibial plateau edge. The implant shouldbe pushed straight back. In some instances, application of valgus stressmay ease insertion of the implant.

To insert the device of FIG. 2 into the lateral compartment amini-incision arthrotomy is performed lateral to the patella tendon.Once the incision is made, the lateral condyle is exposed and a lateralsleeve is prepared to about 1 cm below the joint line using a suitableknife and curved osteotome. After preparing the lateral sleeve, aZ-retractor is placed around the lateral tibial plateau and anteriorportions of the meniscus and the osteophytes along the tibia and femurare removed. The Z-retractor is removed and the implant is placedagainst the distal aspect of the femur and over the tibial plateau edge.The implant is held at a 45° angle and rotated against the lateralcondyle using a lateral to medial push toward the lateral spine. In someinstances, application of varus stress may ease insertion of theimplant.

Once any implant shown in FIG. 2 is implanted, the device should bepositioned within 0 to 2 mm of the AP boundaries of the tibial plateauand superimposed over the boundary. Verification of the range of motionshould then be performed to confirm that there is minimal translation ofthe implant. Once positioning is confirmed, closure of the wound isperformed using techniques known in the art.

As will be appreciated, additional treatment of the surface of thetibial plateau may be desirable, depending on the configuration of theimplant 200. For example, one or more channels or grooves may be formedon the surface of the tibial plateau to accommodate anchoring mechanismssuch as the keel 212 shown in FIG. 2K or the translational movementcross-members 222, 221 shown in FIGS. 2M-N.

B. Condylar Repair Systems

To insert the device 300 shown in FIG. 3, depending on the condyle to berepaired either an antero-medial or antero-lateral skin incision is madewhich begins approximately 1 cm proximal to the superior border of thepatella. The incision typically can range from, for example, 6-10 cmalong the edge of the patella. As will be appreciated, a longer incisionmay be required under some circumstances.

It may be required to excise excess deep synovium to improve access tothe joint. Additionally, all or part of the fat pad may also be excusedand to enable inspection of the opposite joint compartment. Typically,osteophytes are removed from the entire medial and/or lateral edge ofthe femur and the tibia as well as any osteophytes on the edge of thepatella that might be significant.

Although it is possible, typically the devices 300 do not requireresection of the distal femur prior to implanting the device. However,if desired, bone cuts can be performed to provide a surface for theimplant.

At this juncture, the patient's leg is placed in 90° flexion position. Aguide can then be placed on the condyle which covers the distal femoralcartilage. The guide enables the surgeon to determine placement ofapertures that enable the implant 300 to be accurately placed on thecondyle. With the guide in place, holes are drilled into the condyle tocreate apertures from 1-3 mm in depth. Once the apertures have beencreated, the guide is removed and the implant 300 is installed on thesurface of the condyle. Cement can be used to facilitate adherence ofthe implant 300 to the condyle.

Where more than one condyle is to be repaired, e.g., using two implants300 of FIG. 3, or the implant 400 of FIG. 4, or where a condyle and aportion of the patellar surface is to be repaired, e.g., using theimplant 500 of FIG. 5, the surgical technique described herein would bemodified to, for example, provide a greater incision for accessing thejoint, provide additional apertures for receiving the pegs of theimplant, etc.

C. Patellar Repair System

To insert the device shown in FIG. 7, it may be appropriate to use theincisions made laterally or medially to the patella tendon and describedabove with respect to FIG. 2. First the patella is everted laterally andthe fat pad and synovium are bent back from around the periphery of thepatella. If desired, osteophytes can be removed. Prior to resurfacingthe natural patella 620, the knee should be manually taken throughseveral ranges of motion maneuvers to determine whether subluxation ispresent. If subluxation is present, then it may be necessary tomedialize the implant 600. The natural patella can then be cut in aplanar, or flat, manner such that a flat surface is presented to theimplant. The geometric center of the patella 620 is then typicallyaligned with the geometric center of the implant 600. In order to anchorthe implant 600 to the patella 620, one or more holes or apertures canbe created in the patellar surface to accept the pegs 610 of the implant600.

VI. Kits

One or more of the implants described above can be combined together ina kit such that the surgeon can select one or more implants to be usedduring surgery.

This description is not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and the generic principlesdefined herein can be applied to other embodiments and applicationswithout departing from the spirit and scope as defined by the appendedclaims. The application of the concepts and principals extends beyondthe specific embodiments described herein, which can be modified to suitparticular uses contemplated, and entirely different embodiments arepossible that will employ some or all of the principles described andhave some, all or different advantages than those described herein.Methods recited herein may be carried out in any order of the recitedevents which is logically possible, as well as the recited order ofevents. Where a range of values is provided, it is understood that everyintervening value, between the upper and lower limit of that range andany other stated or intervening value in that stated range isencompassed. Also, it is contemplated that any optional feature of theinventive variations described may be set forth and claimedindependently, or in combination with any one or more of the featuresdescribed herein. To the extent necessary to achieve a completeunderstanding disclosed, the specification and drawings of all issuedpatents, patent publications, and patent applications cited in thisapplication are incorporated herein by reference.

What is claimed is:
 1. A method of making an implant for repairing ajoint of a patient, comprising: a. obtaining electronic data regardingmotion of the joint of the patient, wherein the data includesinformation regarding existing geometry or kinematics of the joint ofthe patient, or alternatively, wherein the data includes informationregarding geometry or kinematics of a class of patients; b. using theelectronic data to determine, virtually, a wear pattern of an implantmodel or implant component models selected or designed to repair thejoint of the patient; c. modifying the implant model or implantcomponent models to achieve a revised wear pattern to reduce wear; d.designing a final implant or implant components based on the modifiedimplant model or implant component models.
 2. The method of claim 1,wherein the joint of the patient is a hip joint, a knee joint, an anklejoint, an elbow joint, a shoulder joint, or a spinal joint of thepatient.
 3. The method of claim 1, wherein the revised wear pattern isconfigured to improve motion of the joint of the patient.